JP4011305B2

JP4011305B2 - Wastewater disinfection method and apparatus

Info

Publication number: JP4011305B2
Application number: JP2001151224A
Authority: JP
Inventors: 裕一府中; 栄小三田
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2001-05-21
Filing date: 2001-05-21
Publication date: 2007-11-21
Anticipated expiration: 2021-05-21
Also published as: JP2002346571A

Description

【０００１】
【発明の属する技術分野】
本発明は、大腸菌などを含む排水の消毒方法及び装置に関し、特に、ハロゲン系消毒剤を用いる排水の消毒方法及び装置に関する。本発明によって処理することのできる排水としては、下水、雨天時下水、地表を流下した雨水などを挙げることができる。本発明は、特に、アンモニアを含む雨天時下水などの排水をハロゲン系消毒剤を用いて消毒する方法及び装置に関する。
【０００２】
【従来の技術】
公衆衛生学的観点から、下水、雨水などを含む排水中の病原菌を処理するために、塩素系消毒剤に代表されるハロゲン系消毒剤が古くから用いられている。これらの消毒剤の使用量は少ない方が環境や人類に与える影響が少なく、好ましいことは言うまでもない。しかしながらこれまでは、安全対策上の見地から、病原菌の十分な消毒効果を達成・維持するために、本来必要である消毒剤有効成分濃度を越える過剰な消毒剤を用いてきたのが実情である。
【０００３】
しかし、公共水域に放流される消毒処理後の排水中の残留ハロゲン濃度が高すぎる場合には、公共水域及びその周辺に生育する水棲生物や動植物などの生態系に悪影響を及ぼすことが明らかになるにつれ、適正な消毒剤濃度を排水に添加することが必要であるとの認識を有するに至った。
【０００４】
ところで、排水中の病原菌数は、排水が、家庭排水であるか、産業排水であるか、農業排水であるか、若しくは家庭排水、産業排水、農業排水の含有割合などの発生原因や降雨量の多少など、種々の原因により変動するので、適正な消毒剤投入濃度を決定することは困難である。特に、合流式下水道（家庭汚水及び産業排水と雨水とを同一管に捕集して下水処理場へ送る方式）や、分流式下水道（家庭汚水及び産業排水と雨水とを個別の管に捕集して家庭汚水及び産業排水を下水処理場へ送る方式）における雨天時越流水（雨天時下水）は、非常に短時間で水質が激しく変動するので、適正な消毒剤濃度を決定することが非常に困難である。すなわち、雨天時下水の水質は、降雨の状況により瞬時に大きく変動し、汚水濃度が高く且つ還元性の有機物濃度及び／又は無機物濃度が高い場合と、雨水による希釈が進んで汚水濃度が低下し且つ還元性の有機物濃度及び／又は無機物濃度が低下した場合では、消毒剤の必要量が大きく異なり、水質変動に応じた適切な最少量の消毒剤の添加を行うことが困難である、という問題があった。
【０００５】
【発明が解決しようとする課題】
そこで、本発明は、排水の水質変動に応じて、適正な消毒効果を発揮し且つ残留ハロゲンを発生させないような消毒剤の適正量を求め、この最少必要量の消毒剤を被処理液中に添加する消毒方法及び装置を提供することを目的とする。特に、本発明は、被処理水がアンモニアを含む雨天時下水などの排水の場合であっても、殺菌活性を損なうことなく、最少必要量の消毒剤で被処理水を消毒することができる上述の方法及び装置を提供することを目的とする。なお、雨天時下水とは、雨天時などに下水道設備の処理能力を超える降雨があった場合に、下水道処理設備或いは中継基地であるポンプ所や雨水吐き口から、処理なしに又は簡易処理だけで公共水域に排出する下水をいう。
【０００６】
【課題を解決するための手段】
本発明によれば、被処理液をハロゲン系消毒剤で消毒する方法であって、ハロゲン系消毒剤添加後の有効ハロゲン濃度の減少程度を検知することによってハロゲン系消毒剤の添加量を制御することを特徴とする消毒方法が提供される。
【０００７】
以下、本発明の技術思想を具体例に基づいて説明する。以下の説明は、一具体例を挙げて説明しているもので、本発明はこの記載に限定されるものではない。まず、既設の下水処理施設において、降雨時の種々の時点における合流式下水道越流水を採水してビーカにとり、消毒剤としてBCDMHを用い、消毒剤添加量を３ppm(＝mg/L)としてビーカに加えて、９０秒間消毒処理を行った。降雨開始後の経過時間と消毒処理後の処理水中の大腸菌群数との関係を求めた。結果を図２に示す。
【０００８】
図２から、降雨後３０分経過（Ａ時点）では消毒処理後の大腸菌群数が９０００CFU/mL、降雨後４５分経過（Ｂ時点）では消毒処理後の大腸菌群数が４７００CFU/mLであり、いずれも消毒目標値（水質汚濁防止法に定める放流基準値：３０００CFU/mL以下）を満足しない。降雨後１時間３０分経過（Ｃ時点）で消毒後の大腸菌群数は１０CFU/mL未満となり、消毒目標値以下になったことが分かる。これは、降雨の継続に従って雨天時下水の性状が変化することにより、同じ消毒剤添加量（３ppm）であっても消毒効果が異なり、消毒剤過剰又は消毒剤過小の状態が生じることを示している。即ち、降雨開始直後は、下水中の大腸菌群が高い濃度で流出するため、これを十分に消毒処理するためには多量の消毒剤が必要となるが、降雨開始からある程度時間が経過した時点では、雨水によって汚水が希釈されて排水中の大腸菌群数が減少するため、消毒処理に必要な消毒剤の量が少なくなる。
【０００９】
次に、降雨開始から０．５時間経過後（図２のＡ点）の合流式下水道越流水を採水したものをビーカにとり、BCDMHを種々の添加率で加えて９０秒間消毒処理を行い、処理水中の大腸菌群数を計測した。結果を図３に示す。BCDMH添加率が２ppmでは、消毒処理後の大腸菌群数は１０⁴CFU/mL以上であり、消毒目標値である３０００CFU/mLを満足しない。処理水中の消毒処理後の大腸菌群数は、BCDMH添加率が４ppmでは３０００CFU/mLを僅かに超える程度となり、BCDMH添加率が６ppmでは１００CFU/mL以下となり、消毒目標値を大きく下回った。以上のことから、この時点の下水道越流水の消毒には、４．２〜４．３ppm程度の添加率でBCDMHを加えることが必要なことが分かる。
【００１０】
更に、降雨開始から４５分経過後（図２のＢ点）及び１．５時間経過後（図２のＣ点）についても同様に、BCDMH添加率と、９０秒消毒処理後の大腸菌群数との関係を調べ、結果を図４及び図５に示した。これらの図より、Ｂ点（降雨４５分経過後）では、下水道越流水の消毒に必要なBCDMH添加率は３．５〜３．６ppm程度、Ｃ点（降雨１．５時間経過後）では、下水道越流水の消毒に必要なBCDMH添加率は１．６〜１．７ppm程度であることが分かる。
【００１１】
次に、図２でのＡ点（降雨後３０分経過）、Ｂ点（降雨後４５分経過）及びＣ点（降雨後１．５時間経過）での合流式下水道越流水を採水したものをビーカにとり、BCDMHを図２の実験と同じ添加率３ppmで加え、BCDMH添加後の経過時間と処理水中の残留ハロゲン濃度との関係を調べた。結果を図６に示す。Ａ点（降雨後３０分経過)では、消毒剤添加直後ですでに残留ハロゲン濃度は０．１mg/L as Cl₂未満であり、図２の結果と併せて考えると、BCDMH添加率３ppmでは被処理液の消毒効果は充分でないといえる。Ｂ点（降雨後４５分経過）では、消毒剤添加後約２０秒で残留ハロゲン濃度が約０．１mg/L as Cl₂であり、１００秒でほぼ０mg/L as Cl₂に近いことがわかる。図２の結果（消毒時間９０秒で大腸菌群数が４７００CFU/mL）と併せて考えると、Ｂ時点での消毒剤添加量３ppmは、必要量よりも未だ若干少ないといえる。また、Ｃ時点では、消毒剤添加後約２０秒では残留ハロゲン濃度が０．３mg/L as Cl₂強と高く、約１５０秒まで徐々に低下するが、約１５０秒以降は約０．１mg/L as Cl₂強で安定（消毒作用の飽和）している。これより、Ｃ時点（降雨後１．５時間）での消毒剤の添加量３ppmは過剰で、消毒処理後に残留ハロゲンが残存してしまったことがわかる。
【００１２】
これらの結果を踏まえて、当該下水処理施設の雨天時下水の処理においては、消毒剤処理後の残留ハロゲン濃度を、消毒目標値を確実に達成するための多少の余裕を見て、図６でのＢ線とＣ線のほぼ中間地点に設定すればよい。即ち、図６から、BCDMH添加後２０秒の時点で残留ハロゲン濃度を０．２mg/L as Cl₂に設定すればよい。実際の消毒処理に当たっては、定期的に排水のサンプルを採り、所定濃度の消毒剤を入れて残留ハロゲン濃度の減少程度を測定する。これが上記で設定した設定値（上記の場合には消毒剤添加後２０秒で残留ハロゲン濃度０．２mg/L as Cl₂）よりも高い場合には、排水への消毒剤の投入量を排水サンプルに投入した濃度よりも低い値に調整し、逆に残留ハロゲン濃度の減少程度が設定値よりも低い場合には消毒剤投入量を排水サンプルに投入した濃度よりも高い値に調整する。この作業を定期的に繰り返して、排水への消毒剤の投入量を経時的に制御することにより、消毒剤投入量を、充分な消毒効果が得られ且つ残留ハロゲンが生じない最適値に維持することが可能になる。なお、サンプルに投入する消毒剤の濃度は、その時点で排水中に実際に投入している濃度とすることが好ましい。このようにすれば、消毒剤投入濃度の大きな変動を防ぐことができ、より緻密な制御が可能となるからである。また、サンプルにおいて測定された残留ハロゲン濃度の減少程度と設定値との差から、実際に排水中に投入する濃度をどの程度増減させればよいかについては、当業者が経験的に決定することができる。
【００１３】
なお、図２、図６の曲線は、対象となる下水処理設備が同じであれば、多少の変動はあるがほぼ同様の傾向を示す。したがって、処理対象の下水処理設備において、図２、図６のようなグラフを作成して残留ハロゲン濃度の減少程度の目標値を設定すれば、以降の降雨時には、この設定値に基づいて雨天時下水に対する消毒剤添加量の制御を行うことができる。
【００１４】
次に、本発明の好ましい消毒装置の実施形態を合流式下水処理設備に適用した場合を例にして、本発明の消毒方法の好ましい実施形態を説明する。
合流式下水処理設備は、一般に、一般家庭、事務所、公共施設などの汚水排出源から排出される汚水や雨水を集めて流す下水道管渠、集めた下水を処理場まで送るための中継基地となるポンプ所、送られてきた下水を浄化して河川や海などの放流水域に放流する下水処理場などにより構成されている。下水処理場では、雨天時越流水を沈砂池で一次処理した後、公共水域に放流している。
【００１５】
図１に、本発明の消毒装置の概略説明図を示す。この消毒装置は、被処理液（雨天時越流水）導入ライン２と、消毒槽（沈砂池）３と、被処理液にハロゲン系消毒剤を導入するための消毒剤導入手段４とを備える。消毒剤導入手段４は、消毒槽３の上流のライン２中に導入してもよいし、或いは消毒槽３に直接投入してもよい。また、被処理液導入ライン２の途中に、試験用の被処理液サンプルを採取するための分取ライン１２が接続されている。分取ライン１２には、揚水ポンプ１６が接続されている。
【００１６】
本発明による消毒方法を実施するためには、まず、準備段階として、処理対象となる下水処理設備において、降雨時に、降雨開始から種々の時間が経過した後の複数の越流水サンプルを採取して、これに適当量の消毒剤を加えて消毒後の大腸菌群数を測定することによって、降雨後の経過時間と消毒後の大腸菌群数との関係（図２のグラフ）と、消毒剤添加後の経過時間と被処理水の残留ハロゲン濃度との関係（図６のグラフ）を作成して、これらの関係から、目標とすべき残留ハロゲン減少程度の値を設定しておく。例えば、図２及び図６に示す関係が得られた場合には、上記に説明したように、消毒剤添加後２０秒で残留ハロゲン濃度０．２mg/L as Cl₂という目標値が設定される。
【００１７】
雨天時越流水の消毒は、消毒剤導入手段４から適当量の消毒剤を投入して、消毒槽３で処理することによって行うが、本発明方法においては、消毒剤を添加する前の被処理液を、周期的にライン１２よりサンプリングする。サンプリングされた被処理液は、モニタリング槽１３に収容され、ここで所定量の濃度の消毒剤１４が添加され、撹拌機（図示せず）によって混合撹拌される。モニタリング槽に加える消毒剤の濃度は、緻密な濃度制御を可能にするためには、その時点で消毒剤導入手段４によって被処理液中に実際に供給されている消毒剤の濃度とすることが好ましい。モニタリング槽１３には、被処理液中の残留ハロゲン濃度を測定する測定器１５が接続されており、消毒剤添加後の残留ハロゲン濃度の数値を経時的に測定する。この目的で用いることのできる残留ハロゲン濃度測定器としては、例えば、ポーラログラフ方式による遊離塩素計（例えば、東亜ディーケーケー（株）製造の製品名ＣＬＭ−３７又はＣＬＭ−２２）などを挙げることができる。測定された残留ハロゲン濃度値は記録計１８によって記録される。そして、当該下水処理設備に関して、予め設定されている目標値と、モニタリング槽１３において測定された値とを比較する。例えば、当該下水処理設備に関して図２及び図６のグラフが得られている場合には、設定値は消毒剤添加後２０秒で残留ハロゲン濃度が０．２mg/L as Cl₂という値であるので、モニタリング槽１３で消毒剤が添加された被処理水サンプルの、消毒剤添加後２０秒における残留ハロゲン濃度を測定する。そして、この値が設定値である０．２mg/L as Cl₂よりも高い場合には、消毒剤導入手段４から投入する消毒剤の濃度を減少させ、逆に０．２mg/L as Cl₂よりも低い場合には、消毒剤導入手段４から投入する消毒剤の濃度を増加させる。この消毒剤投入濃度の制御は、予め設定した残留ハロゲン濃度減少程度の目標値を入力したコンピュータ（図示せず）に、残留ハロゲン濃度測定器１５での測定値を通信ラインを通してインプットし、設定値と測定値との比較結果に応じて投入消毒剤量を制御する自動制御装置（図示せず）を用いることにより、自動的に行うことができる。残留ハロゲン濃度減少程度の測定が完了した被処理水サンプルは、戻しライン１７を介して被処理液導入ライン２に戻し、被処理液と共に消毒槽３に導入する。消毒槽３では、消毒剤が加えられた被処理液が短い場合には１分以内、長い場合には１０分以内滞留されて、消毒剤との反応が進められる。消毒処理が行われた被処理水は、ポンプ６により揚水されて、排水路７を介して、公共水域８に放流される。
【００１８】
なお、被処理液サンプルは、消毒剤投入位置よりも上流から採取することが好ましい。消毒剤投入位置よりも下流からサンプルを採取する、即ち消毒剤が添加されている被処理液をサンプルとして採取すると、消毒途中のある時点での残留ハロゲン濃度を測定することになるが、図６に示したように、残留ハロゲン濃度は消毒剤添加後の経過時間に極めて敏感に依存して変化するので、これでは適切な制御はできないからである。
【００１９】
本発明によれば、上記のモニタリング操作を、定期的、例えば１分〜６０分毎、好ましくは５分〜２０分毎に行い、その結果に応じて消毒剤の添加濃度を調整する。これによって、特に時間の経過によってその性状が大きく変動する雨天時越流水の消毒処理に際して、充分な消毒効果を与えると共に、残留ハロゲンを公共用水域に放出することのない、適切な消毒剤添加濃度を維持することが可能になる。
【００２０】
なお、雨天時越流水などの排水の消毒においては、消毒剤の添加量は、消毒剤の種類や排水の性状などによっても変化するが、一般に１〜１０mg/L(ppm)、好ましくは２〜６mg/Lであり、本発明においても、この範囲内で消毒剤添加量を制御することが好ましい。
【００２１】
本発明により消毒することができる被処理液としては、下水、雨水を含む下水、及び地表を流下した雨水等を含む排水などを挙げることができる。特に、アンモニアを含む排水、具体的には雨天時越流水などが特に好ましい。
【００２２】
本発明方法において用いることのできる消毒剤としては、下水や排水の消毒に用いることのできる任意のハロゲン系消毒剤を用いることができる。しかしながら、雨天時越流水などに見られるように、処理すべき排水（被処理水）がアンモニアを含む場合には、塩素系消毒剤中の塩素とアンモニアとが反応して、クロラミンを形成し、殺菌力を低下させるので、アンモニアを含まない被処理水に対する場合よりも多量の塩素系消毒剤が必要であり、クロラミンの残留性が高いため、残留塩素濃度も高くなる、という問題があった。この問題を解決するためには、消毒剤として、本発明者らが先に提案した臭素系又はヨウ素系の消毒剤を用いることが特に好ましい。
【００２３】
本発明において特に好適に用いることのできる臭素系又はヨウ素系消毒剤としては、例えば、ヒダントイン類、シアヌール酸類、イソチアゾロン類、ε−カプロラクタム類、フタールイミド類、ピロリドン類、アクリドン類、ウラシル類、スクシンイミド類、バルビツール類、クレアチニン類、ジオキソピペラジン類、ウラゾール類、グリシン無水物類、ω−ヘプタラクタム類、マレイン酸ヒドラジド類、マレイン酸イミド類、オクタラクタム類、オキシインドール類などを好ましく挙げることができる。これらの構造式を下記に示す。
【００２４】
【化１】

【００２５】
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。
【００２６】
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。
【００２７】
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。
【００２８】
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。
【００２９】
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。
【００３０】
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。
【００３１】
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。
【００３２】
【化２】

【００３３】
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。
【００３４】
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。
【００３５】
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。
【００３６】
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。
【００３７】
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。
【００３８】
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。
【００３９】
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。
【００４０】
【化３】

【００４１】
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。
【００４２】
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。
【００４３】
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。
【００４４】
【化４】

【００４５】
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。
【００４６】
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。
【００４７】
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。
【００４８】
【実施例】
実施例１
図２〜図６を作成した下水処理施設における雨天時越流水について、本発明方法による消毒処理を実施した。消毒装置は、図１に示す構成の装置を用いた。消毒剤としては、BCDMHを用いた。消毒剤導入手段４からの消毒剤の投入による消毒処理を行いながら、１０分に１回の頻度でサンプリングライン１２から被処理液のサンプルを採取してモニタリング槽１３に導入し、所定濃度の消毒剤１４を加えた。ここで加える消毒剤１４の濃度は、その時点において消毒剤導入手段４から被処理液中に投入されている消毒剤濃度とした。なお、消毒処理開始時の消毒剤濃度は５mg/Lとした。モニタリング槽内の被処理液サンプルにBCDMHを添加した20秒後の時点での被処理液サンプル中の残留ハロゲン濃度を測定器１５によって測定し、測定値が0.2 mg/L as Cl₂よりも高い場合には消毒剤導入手段４から加える消毒剤の濃度を減少させ、測定値が０．２mg/L as Cl₂よりも低い場合には消毒剤導入手段４から加える消毒剤の濃度を増加させた。このように１０分毎に消毒剤投入濃度の調整を行いながら消毒処理を継続し、１５分ごとに排出液中の大腸菌群数を計測した。結果を図７に示す。この結果から、消毒剤添加量が時間と共に変化し、一方、被処理後の排水中の大腸菌群数は消毒目標値（３０００CFU/mL）以下で維持できていたことが分かる。
【００４９】
【発明の効果】
本発明によれば、雨天時越流水など大腸菌群数が激変する被処理液に対するハロゲン系消毒剤の添加量を短時間に調節可能で、十分な消毒効果を得ながら過剰添加を抑え、公共水域への過剰なハロゲン系消毒剤の放出を防止することができる。
【図面の簡単な説明】
【図１】図１は、本発明の消毒装置の概略説明図である。
【図２】図２は、下水処理設備における雨天時越流水に対して所定量のハロゲン系消毒剤を添加した際の、降雨後経過時間と消毒後大腸菌群数の関係とを示すグラフである。
【図３】図３は、降雨後０．５時間経過後（図２のＡ点）での雨天時下水に対して種々の濃度のハロゲン系消毒剤を添加した場合の、消毒後の大腸菌群数を示すグラフである。
【図４】図４は、降雨後４５分経過後（図２のＢ点）での雨天時下水に対して種々の濃度のハロゲン系消毒剤を添加した場合の、消毒後の大腸菌群数を示すグラフである。
【図５】図５は、降雨後１．５時間経過後（図２のＣ点）での雨天時下水に対して種々の濃度のハロゲン系消毒剤を添加した場合の、消毒後の大腸菌群数を示すグラフである。
【図６】図６は、種々の降雨後経過時間における雨天時越流水に対してハロゲン系消毒剤を添加した場合の、消毒剤添加後経過時間と被処理液中の残留ハロゲン濃度との関係を示すグラフである。
【図７】本発明方法にしたがって、消毒剤の添加量を制御して雨天時越流水に対して消毒処理を行った実施例において、消毒剤添加量と大腸菌群数の変化を降雨後の経過時間に対して実測した結果を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sterilization method and apparatus for wastewater containing Escherichia coli and the like, and more particularly to a sterilization method and apparatus for wastewater using a halogen-based disinfectant. Examples of the wastewater that can be treated according to the present invention include sewage, sewage in rainy weather, and rainwater flowing down the surface of the earth. In particular, the present invention relates to a method and an apparatus for disinfecting wastewater such as sewage in the rain containing ammonia using a halogen-based disinfectant.
[0002]
[Prior art]
From the viewpoint of public health, halogen-based disinfectants represented by chlorine-based disinfectants have long been used to treat pathogens in wastewater including sewage and rainwater. Needless to say, it is preferable to use less of these disinfectants because they have less influence on the environment and mankind. However, until now, from the viewpoint of safety measures, in order to achieve and maintain a sufficient disinfecting effect of pathogenic bacteria, it has been the actual situation that an excessive disinfectant exceeding the concentration of the active ingredient of the disinfectant originally necessary has been used. .
[0003]
However, it is clear that if the residual halogen concentration in the wastewater after disinfection discharged into public water areas is too high, it adversely affects ecosystems such as aquatic organisms and animals and plants that grow in and around public water areas. As a result, it has been recognized that it is necessary to add an appropriate concentration of disinfectant to the waste water.
[0004]
By the way, the number of pathogenic bacteria in the wastewater can be calculated based on whether the wastewater is domestic wastewater, industrial wastewater, agricultural wastewater, Since it varies depending on various causes such as some, it is difficult to determine an appropriate disinfectant concentration. In particular, combined sewers (methods for collecting domestic sewage and industrial wastewater and rainwater in the same pipe and sending them to a sewage treatment plant) and split sewers (collecting domestic sewage, industrial wastewater and rainwater in separate pipes) In the case of rainwater overflow (rainwater during rainy weather) in the method of sending domestic sewage and industrial wastewater to sewage treatment plants), it is very important to determine the appropriate disinfectant concentration because the water quality fluctuates drastically in a very short time. It is difficult to. In other words, the quality of sewage in rainy weather varies greatly depending on the rain conditions, and when the sewage concentration is high and the concentration of reducing organic and / or inorganic substances is high, dilution with rainwater proceeds and the sewage concentration decreases. When the reducing organic substance concentration and / or inorganic substance concentration is reduced, the necessary amount of the disinfectant varies greatly, and it is difficult to add an appropriate minimum amount of disinfectant according to the water quality fluctuation. was there.
[0005]
[Problems to be solved by the invention]
Therefore, the present invention obtains an appropriate amount of a disinfectant that exhibits an appropriate disinfecting effect and does not generate residual halogen according to the water quality fluctuation of the waste water, and this minimum amount of disinfectant is contained in the liquid to be treated. It aims at providing the disinfection method and apparatus to add. In particular, the present invention is capable of disinfecting water to be treated with a minimum amount of disinfectant without impairing sterilization activity even when the water to be treated is drainage such as sewage in the rain containing ammonia. It is an object of the present invention to provide a method and apparatus. In the case of rainy weather, sewage can be used without any treatment or by simple treatment from the sewerage treatment facility or the pumping station that is a relay base or rainwater outlet when there is rainfall that exceeds the treatment capacity of the sewerage facility. Sewage discharged into public water areas.
[0006]
[Means for Solving the Problems]
According to the present invention, there is a method for disinfecting a liquid to be treated with a halogen-based disinfectant, and the addition amount of the halogen-based disinfectant is controlled by detecting the degree of decrease in the effective halogen concentration after the addition of the halogen-based disinfectant. There is provided a disinfecting method characterized in that.
[0007]
Hereinafter, the technical idea of the present invention will be described based on specific examples. The following description is given with a specific example, and the present invention is not limited to this description. First, in an existing sewage treatment facility, the combined sewer overflow at various times during the rain is sampled into a beaker, BCDMH is used as the disinfectant, and the disinfectant addition amount is 3 ppm (= mg / L). In addition, the sterilization treatment was performed for 90 seconds. The relationship between the elapsed time after the start of rainfall and the number of coliform bacteria in the treated water after disinfection was obtained. The results are shown in FIG.
[0008]
From FIG. 2, the number of coliforms after disinfection is 9000 CFU / mL after 30 minutes after rain (A time point), and the number of coliform groups after disinfection is 4700 CFU / mL after 45 minutes after rain (time B). Neither of them satisfies the disinfection target value (release standard value stipulated in the Water Pollution Control Law: 3000 CFU / mL or less). It can be seen that the number of coliform bacteria after sterilization became less than 10 CFU / mL after 1 hour and 30 minutes after raining (time point C), which was below the sterilization target value. This shows that the disinfection effect is different even if the amount of sewage in rainy weather changes as rain continues, even if the same disinfectant addition amount (3 ppm), and the disinfectant excess or disinfectant understate occurs. Yes. That is, immediately after the start of rainfall, coliform bacteria in the sewage flow out at a high concentration, so a large amount of disinfectant is necessary to fully disinfect this, but at the time when a certain amount of time has passed since the start of rainfall. Since sewage is diluted by rainwater and the number of coliforms in the wastewater is reduced, the amount of disinfectant required for disinfection is reduced.
[0009]
Next, 0.5 hours after the start of rainfall (point A in FIG. 2), the collected sewage overflow water was collected into a beaker, BCDMH was added at various addition rates, and sterilized for 90 seconds. The number of coliforms in the treated water was counted. The results are shown in FIG. When the BCDMH addition rate is 2 ppm, the number of coliform bacteria after disinfection is 10 ⁴ CFU / mL or more, which does not satisfy the disinfection target value of 3000 CFU / mL. The number of coliforms after disinfection in the treated water was slightly over 3000 CFU / mL when the BCDMH addition rate was 4 ppm, and was below 100 CFU / mL when the BCDMH addition rate was 6 ppm, which was significantly below the target disinfection value. From the above, it can be understood that BCDMH needs to be added at an addition rate of about 4.2 to 4.3 ppm for disinfection of sewer overflows at this point.
[0010]
Further, after 45 minutes from the start of rainfall (point B in FIG. 2) and after 1.5 hours (point C in FIG. 2), the BCDMH addition rate and the number of coliforms after 90 seconds of disinfection were similarly determined. And the results are shown in FIG. 4 and FIG. From these figures, at point B (after 45 minutes of rainfall), the BCDMH addition rate required for disinfection of sewer overflow water is about 3.5 to 3.6 ppm, and at point C (after 1.5 hours of rainfall), It can be seen that the BCDMH addition rate required for disinfection of sewer overflows is about 1.6 to 1.7 ppm.
[0011]
Next, sampled combined sewer overflow at point A (30 minutes after rain), point B (45 minutes after rain) and point C (1.5 hours after rain) in Figure 2 Was added to a beaker, BCDMH was added at the same addition rate of 3 ppm as in the experiment of FIG. 2, and the relationship between the elapsed time after the addition of BCDMH and the residual halogen concentration in the treated water was examined. The results are shown in FIG. At point A (30 minutes after the rain), the residual halogen concentration was already less than 0.1 mg / L as Cl ₂ immediately after the disinfectant was added. Considering the results shown in FIG. It can be said that the disinfection effect of the treatment liquid is not sufficient. At point B (45 minutes after rain), the residual halogen concentration is about 0.1 mg / L as Cl ₂ after about 20 seconds after adding the disinfectant, and it is close to almost 0 mg / L as Cl ₂ after 100 seconds. . Considering together with the result of FIG. 2 (disinfection time 90 seconds and the number of coliforms is 4700 CFU / mL), it can be said that the amount of the disinfectant addition 3 ppm at time B is still slightly less than the required amount. In addition, at time C, the residual halogen concentration is as high as 0.3 mg / L as Cl ₂ at about 20 seconds after addition of the disinfectant and gradually decreases to about 150 seconds, but after about 150 seconds, it is about 0.1 mg / L. L as Cl _{2 is} strong and stable (saturation of disinfection action). From this, it can be seen that the amount of addition of 3 ppm of the disinfectant at the time point C (1.5 hours after the rain) was excessive, and residual halogen remained after the disinfection treatment.
[0012]
Based on these results, in the treatment of sewage in rainy weather at the sewage treatment facility, the residual halogen concentration after the disinfectant treatment is shown in FIG. 6 with a slight margin for reliably achieving the disinfection target value. What is necessary is just to set to the substantially halfway point of B line and C line. That is, from FIG. 6, the residual halogen concentration may be set to 0.2 mg / L as Cl ₂ 20 seconds after the addition of BCDMH. In actual disinfection treatment, drainage samples are taken periodically, a predetermined concentration of disinfectant is added, and the degree of decrease in residual halogen concentration is measured. If this is higher than the set value set above (in this case, the residual halogen concentration 0.2 mg / L as Cl ₂ 20 seconds after adding the disinfectant), the amount of disinfectant input to the wastewater is set to the drainage sample. The concentration is adjusted to a value lower than the concentration input to the sample, and conversely, if the degree of decrease in the residual halogen concentration is lower than the set value, the disinfectant input amount is adjusted to a value higher than the concentration input to the drainage sample. By periodically repeating this operation and controlling the amount of disinfectant input to the waste water over time, the amount of disinfectant input is maintained at an optimum value at which a sufficient disinfecting effect is obtained and no residual halogen is generated. It becomes possible. In addition, it is preferable that the concentration of the disinfectant to be added to the sample is a concentration actually added to the waste water at that time. This is because a large variation in the concentration of the disinfectant can be prevented and more precise control can be performed. In addition, from the difference between the decrease in residual halogen concentration measured in the sample and the set value, the person skilled in the art will empirically determine how much the concentration actually put into the wastewater should be increased or decreased. Can do.
[0013]
The curves in FIGS. 2 and 6 show almost the same tendency although there are some fluctuations if the target sewage treatment facilities are the same. Accordingly, in the sewage treatment facility to be treated, if graphs as shown in FIG. 2 and FIG. 6 are created and a target value for reducing the residual halogen concentration is set, then it will be rained on the basis of this set value during subsequent rainfall. The amount of disinfectant added to the sewage can be controlled.
[0014]
Next, a preferred embodiment of the disinfection method of the present invention will be described by taking as an example the case where a preferred embodiment of the disinfection apparatus of the present invention is applied to a combined sewage treatment facility.
A combined sewage treatment facility generally has a sewer pipe for collecting and flowing sewage and rainwater discharged from sewage discharge sources such as ordinary households, offices, and public facilities, and a relay base for sending the collected sewage to the treatment plant. It consists of a sewage treatment plant that purifies the sewage that has been sent and discharges it into a discharge area such as a river or the sea. In the sewage treatment plant, the rainwater overflowing water is primarily treated in a sand basin and then discharged into public water bodies.
[0015]
In FIG. 1, the schematic explanatory drawing of the disinfection apparatus of this invention is shown. This disinfecting apparatus comprises a liquid to be treated (rainy overflow water) introduction line 2, a disinfecting tank (sedimentation basin) 3, and a disinfectant introducing means 4 for introducing a halogen-based disinfectant into the liquid to be treated. The disinfectant introduction means 4 may be introduced into the line 2 upstream of the disinfection tank 3 or may be directly introduced into the disinfection tank 3. Further, a preparative line 12 for collecting a test liquid sample to be tested is connected to the process liquid introduction line 2. A pumping pump 16 is connected to the sorting line 12.
[0016]
In order to carry out the disinfection method according to the present invention, first, as a preparation stage, in a sewage treatment facility to be treated, at the time of raining, a plurality of overflow water samples after various times have elapsed since the start of rainfall are collected. By adding an appropriate amount of disinfectant and measuring the number of coliform bacteria after disinfection, the relationship between the elapsed time after rainfall and the number of coliform bacteria after disinfection (graph in Fig. 2) and after addition of disinfectant The relationship between the elapsed time and the residual halogen concentration of the water to be treated (graph of FIG. 6) is created, and the value of the degree of residual halogen reduction to be targeted is set from these relationships. For example, when the relationship shown in FIGS. 2 and 6 is obtained, as described above, a target value of a residual halogen concentration of 0.2 mg / L as Cl ₂ is set 20 seconds after the addition of the disinfectant. .
[0017]
Disinfection of rainwater flowing over rainy weather is performed by introducing an appropriate amount of disinfectant from the disinfectant introduction means 4 and processing in the disinfecting tank 3, but in the method of the present invention, the treatment target before adding the disinfectant is performed. The liquid is sampled periodically from line 12. The sampled liquid to be treated is stored in the monitoring tank 13, where a predetermined amount of the disinfectant 14 is added, and mixed and stirred by a stirrer (not shown). In order to enable precise concentration control, the concentration of the disinfectant added to the monitoring tank may be the concentration of the disinfectant actually supplied into the liquid to be treated by the disinfectant introduction unit 4 at that time. preferable. The monitoring tank 13 is connected with a measuring instrument 15 for measuring the residual halogen concentration in the liquid to be treated, in a time measured through the value of the residual halogen concentration after disinfectant added. Examples of the residual halogen concentration measuring instrument that can be used for this purpose include a polarographic free chlorine meter (for example, product name CLM-37 or CLM-22 manufactured by Toa DKK Co., Ltd.). The measured residual halogen concentration value is recorded by the recorder 18. And regarding the said sewage treatment equipment, the preset target value and the value measured in the monitoring tank 13 are compared. For example, when the graphs of FIGS. 2 and 6 are obtained for the sewage treatment facility, the set value is a value of 0.2 mg / L as Cl ₂ after 20 seconds after the addition of the disinfectant. Then, the residual halogen concentration of the treated water sample to which the disinfectant is added in the monitoring tank 13 is measured 20 seconds after the disinfectant is added. If this value is higher than the set value of 0.2 mg / L as Cl ₂ , the concentration of the disinfectant introduced from the disinfectant introduction means 4 is decreased, and conversely 0.2 mg / L as Cl _2. If lower than that, the concentration of the disinfectant introduced from the disinfectant introduction means 4 is increased. The control of the concentration of the disinfectant is performed by inputting the measurement value of the residual halogen concentration measuring device 15 through a communication line to a computer (not shown) that has input a target value for decreasing the residual halogen concentration set in advance. This can be done automatically by using an automatic control device (not shown) that controls the amount of the disinfectant input according to the comparison result between the measured value and the measured value. The treated water sample for which the measurement of the degree of residual halogen concentration reduction has been completed is returned to the treated liquid introduction line 2 via the return line 17 and introduced into the disinfection tank 3 together with the treated liquid. In the disinfection tank 3, the liquid to be treated to which the disinfectant is added is retained within 1 minute when the liquid to be treated is short, and within 10 minutes when it is long, and the reaction with the disinfectant proceeds. The treated water that has been sterilized is pumped by the pump 6 and discharged into the public water area 8 through the drainage channel 7.
[0018]
In addition, it is preferable to collect a liquid sample to be processed from the upstream of the disinfectant input position. When a sample is collected from the downstream of the disinfectant input position, that is, when the liquid to be treated to which the disinfectant is added is collected as a sample, the residual halogen concentration at a certain point during the disinfection is measured. This is because the residual halogen concentration changes very sensitively depending on the elapsed time after the addition of the disinfectant, and thus cannot be controlled appropriately.
[0019]
According to the present invention, the above monitoring operation is performed periodically, for example, every 1 to 60 minutes, preferably every 5 to 20 minutes, and the addition concentration of the disinfectant is adjusted according to the result. As a result, an appropriate disinfectant concentration that gives sufficient disinfecting effects and does not release residual halogens into public water areas, especially when disinfecting rainwater overflowing water, whose properties vary greatly over time. Can be maintained.
[0020]
In addition, in the disinfection of wastewater such as rainwater overflow, the amount of disinfectant added varies depending on the type of disinfectant and the nature of the wastewater, but generally 1 to 10 mg / L (ppm), preferably 2 In the present invention, it is preferable to control the addition amount of the disinfectant within this range.
[0021]
Examples of the liquid to be treated that can be sterilized according to the present invention include sewage, sewage containing rainwater, and drainage containing rainwater flowing down the ground surface. In particular, wastewater containing ammonia, specifically overflow water during rainy weather, is particularly preferable.
[0022]
As the disinfectant that can be used in the method of the present invention, any halogen-based disinfectant that can be used for disinfecting sewage or waste water can be used. However, as seen in rainy weather overflow water etc., when the wastewater to be treated (treated water) contains ammonia, chlorine in the chlorine-based disinfectant reacts with ammonia to form chloramine, Since the sterilizing power is reduced, a larger amount of chlorine-based disinfectant is required than in the case of water to be treated that does not contain ammonia, and there is a problem that the residual chlorine concentration is increased because of the high persistence of chloramine. In order to solve this problem, it is particularly preferable to use the bromine-based or iodine-based disinfectant previously proposed by the present inventors as the disinfectant.
[0023]
Examples of the bromine-based or iodine-based disinfectant that can be particularly preferably used in the present invention include hydantoins, cyanuric acids, isothiazolones, ε-caprolactams, phthalimides, pyrrolidones, acridones, uracils, succinimides. , Barbiturs, creatinines, dioxopiperazines, urazoles, glycine anhydrides, ω-heptalactams, maleic hydrazides, maleic imides, octalactams, oxindoles, etc. it can. These structural formulas are shown below.
[0024]
[Chemical 1]

[0025]
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.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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.
[0031]
Succinimides are represented, for example, by the formula X above. In formula X, X is a bromine atom or an iodine atom.
[0032]
[Chemical 2]

[0033]
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.
[0034]
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.
[0035]
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.
[0036]
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.
[0037]
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.
[0038]
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.
[0039]
Maleic imides (maleimides) are represented, for example, by the above formula XVIII. In formula XVIII, X is a bromine atom or an iodine atom.
[0040]
[Chemical 3]

[0041]
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.
[0042]
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.
[0043]
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.
[0044]
[Formula 4]

[0045]
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.
[0046]
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.
[0047]
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.
[0048]
【Example】
Example 1
The sterilization treatment by the method of the present invention was performed on the rainwater overflowing water in the sewage treatment facility that created FIGS. As the disinfection apparatus, an apparatus having the configuration shown in FIG. 1 was used. BCDMH was used as a disinfectant. While performing the disinfection treatment by introducing the disinfectant from the disinfectant introduction means 4, a sample of the liquid to be treated is sampled from the sampling line 12 at a frequency of once every 10 minutes and introduced into the monitoring tank 13 to disinfect the predetermined concentration. Agent 14 was added. The concentration of the disinfectant 14 added here was the disinfectant concentration that was introduced into the liquid to be treated from the disinfectant introduction means 4 at that time. The concentration of the disinfectant at the start of the disinfection treatment was 5 mg / L. The residual halogen concentration in the sample liquid to be processed 20 seconds after adding BCDMH to the sample liquid to be processed in the monitoring tank is measured by the measuring instrument 15, and the measured value is higher than 0.2 mg / L as Cl ₂ In some cases, the concentration of the disinfectant added from the disinfectant introduction means 4 was decreased, and when the measured value was lower than 0.2 mg / L as Cl ₂ , the concentration of the disinfectant added from the disinfectant introduction means 4 was increased. . Thus, disinfection treatment was continued while adjusting the disinfectant input concentration every 10 minutes, and the number of coliform bacteria in the effluent was measured every 15 minutes. The results are shown in FIG. From this result, it can be seen that the addition amount of the disinfectant changed with time, while the number of coliform bacteria in the wastewater after the treatment was maintained at the disinfection target value (3000 CFU / mL) or less.
[0049]
【The invention's effect】
According to the present invention, it is possible to adjust the amount of halogenated disinfectant added to a liquid to be treated with drastic changes in the number of coliforms such as overflowing water in rainy weather, suppressing excessive addition while obtaining a sufficient disinfecting effect, It is possible to prevent the release of excessive halogen-based disinfectants.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view of a disinfecting apparatus of the present invention.
FIG. 2 is a graph showing the relationship between the elapsed time after rainfall and the number of coliform bacteria after disinfection when a predetermined amount of halogen-based disinfectant is added to rainwater overflow in a sewage treatment facility. .
FIG. 3 shows coliform groups after disinfection when various concentrations of halogen disinfectant are added to sewage in the rain after 0.5 hours have passed since rain (point A in FIG. 2). It is a graph which shows a number.
FIG. 4 shows the number of coliform bacteria after disinfection when various concentrations of halogen-based disinfectant are added to sewage in the rain after 45 minutes from rain (point B in FIG. 2). It is a graph to show.
FIG. 5 shows coliform groups after disinfection when various concentrations of halogen-based disinfectant are added to sewage in the rain after 1.5 hours have elapsed after rain (point C in FIG. 2). It is a graph which shows a number.
FIG. 6 is a graph showing the relationship between the elapsed time after adding a disinfectant and the residual halogen concentration in the liquid to be treated when a halogen-based disinfectant is added to rainwater overflow in various elapsed times after rainfall. It is a graph which shows.
FIG. 7 shows changes in the amount of added disinfectant and the number of coliforms after the rain in an example in which the amount of disinfectant added was controlled according to the method of the present invention to perform disinfection treatment on overflowing water during rainy weather. It is a graph which shows the result actually measured with respect to time.

Claims

A method for disinfecting sewage during rainy weather in a sewage treatment facility,
In this sewage treatment facility, sample the overflow water at the time when various times have passed since the start of rain in rainy weather, add a halogen disinfectant of a predetermined concentration to this, and the elapsed time after the rain and overflow water The relationship between the number of coliforms in the sample and the relationship between the elapsed time after addition of the halogen-based disinfectant and the residual halogen concentration in the overflow water sample was obtained, and from these results, the number of coliforms was below the disinfection target value and Set the target value of the effective halogen concentration in the overflow water sample at a predetermined time after the addition of the halogen-based disinfectant that does not release residual halogen to public water areas ,
In actual disinfection treatment, a sample of overflowing water during rainy weather is collected periodically, a halogenated disinfectant with a predetermined concentration is added to the collected overflowing water sample, and the overflowing water after a predetermined time has elapsed after the addition of the halogenated disinfectant. By measuring the residual halogen concentration in the sample and comparing it with the target value of the effective halogen concentration set above, the amount of halogen-based disinfectant to be added to the sewage in the rainwater treatment facility should be increased or decreased. Feature method.

The target value of the effective halogen concentration in the overflow water sample at the predetermined time point after the addition of the halogen-based disinfectant is after the addition of the halogen-based disinfectant. 20 The residual halogen concentration at the second 0.2mg / L as Cl ₂₂ (In chlorine concentration 0.2mg / L The method according to claim 1, wherein

The predetermined concentration of the halogen-based disinfectant added to the collected overflow water sample is the concentration of the halogen-based disinfectant that is actually added for the disinfection treatment of the overflow water at the time of rain. The method described.

The predetermined concentration of the halogen-based disinfectant added for disinfecting rainwater overflowing water is as follows: 1 ~ 10mg / L The method according to claim 1, wherein

An apparatus for disinfecting sewage in rainwater treatment facilities with a halogen-based disinfectant,
A disinfection tank for disinfecting rainwater sewage by reacting with a halogen-based disinfectant;
A treatment liquid introduction line for introducing the rainwater to the disinfection tank;
Disinfectant introduction means for introducing a halogen-based disinfectant into the disinfection tank ;
And more
A preparative line for collecting a sample of the liquid to be processed before the addition of the halogen-based disinfectant from the liquid introduction line ;
A monitoring tank connected to the preparative line and receiving the sample liquid to be treated;
Disinfectant supply means for adding a predetermined amount of halogen-based disinfectant to the monitoring tank ;
An effective halogen concentration measuring device for measuring the residual halogen concentration of a sample to be treated after a predetermined time has elapsed after addition of the halogen-based disinfectant in the monitoring tank ;
A return line for returning the liquid sample to be treated from the monitoring tank to the disinfection tank;
In the sewage treatment facility, overflow water at the time when various times have elapsed since the start of raining in the rainy weather is taken as a sample, a halogen-based disinfectant with a predetermined concentration is added thereto, and the elapsed time after the rain And the number of coliforms in the overflow water sample, and the relationship between the elapsed time after addition of the halogen-based disinfectant and the residual halogen concentration in the overflow water sample. The target value of the effective halogen concentration in the overflow water sample at a predetermined time point after the addition of the halogen-based disinfectant that is lower than the concentration and does not release residual halogen to public water bodies; actual disinfection treatment In such cases, a sample of overflowing water during rainy weather should be collected periodically in the monitoring tank via the preparative line, and a halogenated disinfectant with a predetermined concentration should be added to the collected overflowing water sample. In addition, by measuring the residual halogen concentration in the overflow water sample at the specified time after the addition of the halogen-based disinfectant and comparing it with the target value of the effective halogen concentration set above, the sewage in the sewage treatment facility A disinfectant addition amount control means for increasing or decreasing the addition amount of the halogen-based disinfectant to be added to the apparatus.