JP3906180B2 - Method for separating phosphorus in organic wastewater - Google Patents

Description

【００４３】
これにより、アンモニア若しくはアンモニウムイオンを除去すると共に、有機性廃水中の有機物を効率的に硝酸態窒素に変換することができるようになる。
【００４４】
また、被処理水中のアンモニア（アンモニウムイオン）は、アノードを構成する電極１０側で発生するオゾン、若しくは、活性酸素と反応Ｅに示す如く反応し、これによっても窒素ガスに脱窒処理される。
反応Ｅ ２ＮＨ₃（ａｑ）＋３（Ｏ）→Ｎ₂↑＋３Ｈ₂Ｏ
【００４５】
これにより、有機物分解処理ステップにて有機物から転換された硝酸態窒素、亜硝酸態窒素及びアンモニア態窒素のうちアンモニア態窒素を除去できると共に、残留有機物を硝酸態窒素まで処理することが可能となる。尚、この場合において、被処理水は、当該有機物分解処理ステップの前段に生物的処理ステップにおいて処理されているため、有機物の分解処理効率が向上し、効果的に、被処理水中の有機物を分解処理することが可能となる。また、本実施例では、被処理水から純度の高いリン化合物を分離するため、有機物分解処理ステップにて被処理水中の有機物を略完全に分解処理することが好ましい。
【００４６】
尚、本実施例において、有機物分解処理装置２に設けられる電極６、７は、両者とも白金／イリジウム電極により構成されているため、所定時間、例えば３０分経過毎にこれらの電極６、７に印加される極性を切り換えることも可能となる。
【００４７】
これにより、カソードを構成する電極７又は６の表面に付着する有機物やスケール（ＣａＣＯ₃、Ｍｇ（ＯＨ）₂等）は、各電極６、７の極性が切り換えられ、当該電極７又は６がアノードとなることにより表面から落とされる。これにより、電極７又は６の電解性能を高く維持できるようになる。
【００４８】
このような有機物の分解処理（有機物分解処理ステップ）の終了後、有機物分解処理槽５内の被処理水を前記窒素及びリン処理装置３の処理槽９内に搬送し、処理槽９内に有機物分解処理された被処理水を貯留する。そして、前記制御装置により電源をＯＮとし、先ず、電極１０に正電位を、電極１１に負電位を印加する（窒素処理ステップ。図２の中段右側）。これにより、電極１０はアノードとなり、電極１１はカソードとなる。
【００４９】
係る電位の印加により、カソードを構成する電極１１側では、アノードを構成する電極１０側において生成された電子が供給され、被処理水中に含まれる硝酸態窒素としての硝酸イオンが亜硝酸イオンに還元される（反応Ｆ）。更に、亜硝酸イオンに還元された硝酸態窒素は、カソードを構成する電極１１側において、電子が供給され、アンモニア（アンモニウムイオン）まで還元される（反応Ｇ）。以下に、反応Ｆ及び反応Ｇを示す。
反応Ｆ ＮＯ₃ ^-＋Ｈ₂Ｏ＋２ｅ^-→ＮＯ₂ ^-＋２ＯＨ^-
反応Ｇ ＮＯ₂ ^-＋５Ｈ₂Ｏ＋６ｅ^-→ＮＨ₃（ａｑ）＋７ＯＨ^-
【００５０】
一方、アノードを構成する白金／イリジウム電極１０側では、被処理水中に含有される塩化物イオンが電子を放出して塩素を生成する。そして、この塩素は水に溶解して次亜塩素酸を生成する。このとき、電極上では同時にオゾン、若しくは、活性酸素も生成される。
【００５１】
ここで、被処理水中に含まれる塩化物イオン濃度が低い場合には、被処理水中に、例えば塩化物イオンや、ヨウ化物イオンや、臭化物イオンなどのハロゲン化物イオンや、これらハロゲン化物イオンを含む化合物、例えば、塩化カリウムや塩化ナトリウムなどを添加してもよい。即ち、被処理水の塩化カリウムの塩化物イオンを例えば１０ｐｐｍ以上４００００ｐｐｍ以下とする。
【００５２】
このような被処理水中に本来含まれる塩化物イオンや上述の如く添加した塩化カリウムは、アノードを構成する電極１０において酸化され、塩素を生成し（前記反応Ｂ。塩化カリウムの場合で示す）、生成された塩素は、被処理水中で水と反応し、次亜塩素酸を生成する（前記反応Ｃ）。そして、生成された次亜塩素酸は、上述の反応Ｇで被処理水中に生成されたアンモニア（アンモニウムイオン）と反応し、複数の化学変化を経た後、窒素ガスに変換される（前記反応Ｄ）。
【００５３】
また、被処理水中のアンモニア（アンモニウムイオン）は、アノードを構成する電極１０側で発生するオゾン、若しくは、活性酸素と前記反応Ｅに示す如く反応し、これによっても窒素ガスに脱窒処理される。
【００５４】
これにより、有機物分解処理ステップにて硝酸態窒素にまで処理された窒素化合物を容易に処理することが可能となる。
【００５５】
上述した如き窒素化合物の処理（窒素処理ステップ）の終了後、制御装置は各電極１０、１１に印加する電位の極性を切り換える（図２の下段。リン処理ステップ。尚、極性切り換え後も被処理水中では上記窒素処理反応が継続している）。これにより、電極１０はカソード、電極１１はアノードを構成することになる。これにより、被処理水は電気化学的手法としての電解処理が行われ、アノードを構成する電極１１は、上述の如く鉄を含む導電体にて構成されていることから、電極１１より鉄（ＩＩ）イオンが被処理水中に溶出して、被処理水中において鉄（ＩＩＩ）イオンにまで酸化される。
【００５６】
生成された鉄（ＩＩＩ）イオンは、反応Ｈに示す如く脱リン反応により、被処理水中のリン酸イオンと凝集沈殿し、水に難溶性のリン酸鉄を生成する。
反応Ｈ Ｆｅ³⁺＋ＰＯ₄ ^3-→ＦｅＰＯ₄↓
これにより、被処理水中に含有されたリン化合物としてのリン酸イオンをリン酸鉄として沈殿処理することができる。
【００５７】
また、電子の供給のために被処理水中に鉄（ＩＩ）イオンの状態で溶出し、電極上或いは被処理水中で酸化された鉄（ＩＩＩ）イオンの一部は、この場合にカソードを構成する電極１０側において、再度電子が供給され、鉄（ＩＩ）イオンに還元されて、硝酸を還元したり、また酸素によって酸化されたりする。
【００５８】
尚、鉄（ＩＩ）イオンを含有した被処理水を電解することにより、被処理水中に含有される硝酸イオンをアンモニウムイオンにまで還元処理する技術については、既に、１９９９年３月１６日から３月１８日に渡って開催された第３３回日本水環境学会において配布された日本水環境学会年会講演集の「電気化学反応を用いた無機窒素化合物処理技術の開発」において開示されている。
【００５９】
尚、本実施例では、窒素処理ステップとリン処理ステップの電気化学的処理は、共通の電極１０、１１を用いて極性切り替えすることにより処理を行っているが、これ以外にも、両者のステップを実行するためのそれぞれの電極を用いても良いものとする。例えば、窒素処理ステップでは、一方の電極及び他方の電極をそれぞれ次亜ハロゲン酸、又は、オゾン、若しくは、活性酸素を発生させることが可能な導電体により構成し、リン処理ステップでは、上記実施例と同様に一方の電極を次亜ハロゲン酸、又は、オゾン、若しくは、活性酸素を発生させることが可能な導電体により構成し、他方の電極を鉄（Ｆｅ）、若しくは、鉄を被覆した導電体により構成しても良いものとする。これにより、窒素処理ステップにおける被処理水の処理効率の向上を図ることができるようになる。
【００６０】
上述した如きリン化合物の処理（リン処理ステップ）の終了後、前記窒素及びリン処理装置３の処理槽９内の被処理水及び沈殿物をろ過処理槽２２に搬送し、ろ過処理槽２２内に窒素・リン処理された後の被処理水及び沈殿物を貯留する。尚、本実施例では、窒素・リン処理装置３の処理槽９とろ過処理槽２２は別槽により構成しているが、同一槽により構成しても良いものとする。
【００６１】
ろ過処理槽２２において図示しない制御装置により前記ブロワー２８及び吸引ポンプが運転されると、ろ過処理槽２２内の被処理水中の水分のみが微孔性薄膜２４の膜体３０内にろ過される。このとき、被処理水中に含まれる水に難溶性のリン酸鉄は、膜体３０の表面に付着する。
【００６２】
微孔性薄膜２４の膜体３０内に吸引された被処理水は、膜体３０を通過することで、リン酸鉄と分離され、その後、スペーサー３２及び支持体３４を経て集水出口３６に到達し、前記吸引ポンプにより外部へ排出される。
【００６３】
他方、微孔性薄膜２４の表面に付着したリン酸鉄はブロワー２８から発生する気泡によってエアレーション洗浄され、微孔性薄膜２４から剥離され、ろ過処理槽２２内を浮遊し、ろ過処理槽２２内下部に沈積する。当該沈積したリン酸鉄を回収することにより、容易に純度の高いリン化合物を得ることができる。
【００６４】
以上詳述した如く本実施例では、被処理水は、ＣＯＤ又はＢＯＤ低減処理ステップにて一旦、被処理水中に含有される有機物のＣＯＤ又はＢＯＤを低減処理した後、窒素処理ステップにて被処理水中に含有される窒素化合物を処理し、リン処理ステップにて被処理水中に含有されるリン化合物を沈殿処理するため、リン化合物分離処理ステップにて容易に被処理水中のリン化合物を分離できるようになる。
【００６５】
特に、リン化合物分離処理ステップにおける被処理水中には、前段のＣＯＤ又はＢＯＤ低減処理ステップにおいて有機物が低減されているため、リン化合物に有機物が取り込まれた状態で当該リン化合物が分離される不都合を著しく抑制することができる。
【００６６】
これにより、分離されたリン化合物中に例えば毒性を有する有機物が取り込まれる可能性を著しく低減することができ、当該リン化合物を肥料として好適な状態で再利用することができるようになる。
【００６７】
また、ＣＯＤ又はＢＯＤ低減処理ステップにて、被処理水中に含有される有機物のＣＯＤ又はＢＯＤを略完全に分解処理した場合には、リン処理ステップにおいて沈殿するリン化合物（リン酸鉄）は、有機物がほぼ含有されていないため、リン化合物分離処理ステップにおいて分離されるリン化合物（リン酸鉄）内に有機物が含有される不都合を回避することができるようになり、より純度の高いリン化合物として再利用することが可能となる。これにより、有機性廃水から得られるリン化合物の再利用価値の向上を図ることができるようになる。
【００６８】
尚、本実施例において回収されるリン化合物はリン酸鉄であるため、例えばマメ科の植物の肥料として使用する場合には、その後、格別な処理を行うことなく使用することが可能となる。その他の植物などに肥料として用いる場合には、リンの吸収性を向上させるため鉄を除去する必要がある。その場合には、例えばリンゴ酸やクエン酸などの有機酸を用いて当該リン酸鉄を溶解し、鉄を除去した状態で肥料として使用することが好ましい。
【００６９】
【発明の効果】
以上詳述した如く本発明によれば、有機性廃水中の有機物を処理するＣＯＤ又はＢＯＤ低減処理ステップと、該ＣＯＤ又はＢＯＤ低減処理ステップ終了後、電気化学的手法により有機性廃水中の窒素化合物を処理する窒素処理ステップと、該窒素処理ステップの終了後、電気化学的手法により有機性廃水中のリン化合物を処理するリン処理ステップと、該リン処理ステップの終了後、有機性廃水中のリン化合物を分離するリン化合物分離処理ステップとを含むので、ＣＯＤ又はＢＯＤ低減処理ステップにて一旦、有機性廃水中に含有される有機物のＣＯＤ又はＢＯＤを低減させた後、窒素処理ステップにて有機性廃水中に含有される窒素化合物を処理し、リン処理ステップにて有機性廃水中に含有されるリン化合物を処理することができるようになる。その後、リン化合物分離処理ステップにて有機性廃水中のリン化合物を分離できるようになる。
【００７０】
ここで、リン化合物分離処理ステップにおける有機性廃水中には、前段のＣＯＤ又はＢＯＤ低減処理ステップにおいて有機物が低減されているため、リン化合物に有機物が取り込まれた状態で当該リン化合物が分離される不都合を著しく抑制することができる。
【００７１】
これにより、分離されたリン化合物中に例えば毒性を有する有機物が取り込まれる可能性を著しく低減することができ、当該リン化合物を肥料として好適な状態で再利用することができるようになる。
【００７２】
また、本発明では、請求項２の発明の如く窒素処理ステップとリン処理ステップにおける電気化学的手法に用いる一方の電極を次亜ハロゲン酸、又は、オゾン、若しくは、活性酸素を発生させることが可能な導電体とし、他方の電極を鉄を含む導電体とすると共に、窒素処理ステップにおいて一方の電極をアノード、他方の電極をカソードとするため、当該窒素処理ステップにおいてアノードから発生される次亜ハロゲン酸、又は、オゾン、若しくは、活性酸素等の酸化剤により効果的に有機性廃水中の窒素化合物を処理することができるようになる。
【００７３】
また、リン処理ステップにおいて一方の電極をカソード、他方の電極をアノードとするため、当該リン処理ステップにおいて、アノードとなる他方の電極より有機性廃水中に鉄（ＩＩ）イオンを溶出させ、有機性廃水中で鉄（ＩＩＩ）イオンにまで酸化された当該鉄（ＩＩＩ）イオンと有機性廃水中のリン化合物としてのリン酸イオンを化学的に反応させ、リン酸鉄として沈殿処理することができるようになる。
【００７４】
これにより、リン化合物分離処理ステップにおいて、リン化合物をリン酸鉄として分離することができるようになる。
【００７５】
また、請求項３の発明によれば、上記各発明に加えて、リン化合物分離処理ステップを、微孔性薄膜により構成され、当該微孔性薄膜を介して有機性廃水をろ過することにより、有機性廃水中のリン化合物を分離するろ過処理手段により実行するため、有機性廃水からリン化合物を分離することができるようになる。
【００７６】
請求項４の発明によれば、上記各発明において、ＣＯＤ又はＢＯＤ低減処理ステップは、有機性廃水中に一対の電極を一部浸漬し、電気化学的手法により有機性廃水中の有機物を分解処理する有機物分解処理ステップを含むので、有機性廃水中の有機物を効果的に硝酸態窒素に変換することができるようになる。これにより、後段における窒素処理ステップにおいて、窒素化合物の処理効率の向上を図ることができるようになる。
【００７７】
また、請求項５の発明の如くＣＯＤ又はＢＯＤ低減処理ステップは、有機物分解処理ステップの前段に生物的処理ステップを含むことにより、一旦、生物的処理ステップにて有機性廃水中の有機物を分解除去した後、有機物分解処理ステップを行うことができるようになり、より一層、ＣＯＤ又はＢＯＤ低減処理ステップを効率的に行うことができるようになる。
【００７８】
請求項６の発明によれば、上記各発明において、ＣＯＤ又はＢＯＤ低減処理ステップは、有機性廃水中の有機物を略完全に分解処理するので、後段におけるリン化合物分離処理ステップにおいて分離されるリン化合物内に有機物が含有される不都合を回避することができるようになり、純度の高いリン化合物として再利用することが可能となる。
【図面の簡単な説明】
【図１】本発明の有機性廃水中のリン分離方法を実現するための処理システムの概要を示す説明図である。
【図２】生物的処理槽と、有機物分解処理装置と、窒素及びリン処理装置の概要を示す説明図である。
【図３】リン化合物分離処理装置の概略断面図である。
【図４】微孔性薄膜の斜視図である。
【符号の説明】
１ 処理システム
２ 有機物分解処理装置
３ 窒素及びリン処理装置
４ 処理室
５ 有機物分解処理槽
６、７、１０、１１ 電極
８ 処理室
９ 窒素及びリン処理槽
１２ 生物的処理槽
１５ ろ過処理装置
２２ ろ過処理槽
２４ 微孔性薄膜
３０ 膜体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for separating phosphorus from organic wastewater discharged from, for example, livestock farmers, particularly organic wastewater containing phosphorus compounds such as phosphoric acid and phosphate ions.
[0002]
[Prior art]
Conventionally, it is well known that the presence of nitrogen compounds and phosphorus compounds is one of the causes of eutrophication of rivers and lakes. In addition, these phosphorus compounds and nitrogen compounds are abundant in domestic household effluents, factory effluents, and organic wastewater such as livestock farmers, but are difficult to purify and effective measures can be taken. There is no current situation. In particular, organic wastewater discharged from livestock producers such as pig farmers contains a lot of organic matter with high COD (chemical oxygen demand) or BOD (biological oxygen demand), and purification treatment is It was very difficult.
[0003]
Generally, phosphorus compounds contained in organic wastewater are recovered and reused as insoluble phosphorus compounds. As a method for converting a phosphorus compound in organic wastewater into a phosphorus compound that is sparingly soluble in water, for example, there are four methods. The first method is to recover a phosphorus compound from organic wastewater as MAP (Magnesium Ammonium Phosphate). This is a phosphorus compound formed in equimolar amounts of magnesium, ammonium and phosphate ions in organic wastewater under high pH conditions.
[0004]
The second method is a fostrip method that allows microorganisms to incorporate phosphoric acid in organic wastewater. This method removes phosphoric acid in organic wastewater by taking advantage of the characteristics of certain microorganisms in which the amount of phosphate uptake under aerobic conditions exceeds the amount of phosphate released under anaerobic conditions. And a phosphorus compound is collect | recovered as calcium phosphate by adding a calcium agent after the re-release of the phosphoric acid by microorganisms or destruction of microorganisms.
[0005]
The third method uses an iron material or an aluminum material for the cathode to electrically elute iron ions or aluminum ions into the organic wastewater, and converts the phosphate ions in the organic wastewater into insoluble iron phosphate or It is a method of carrying out precipitation treatment as aluminum phosphate.
[0006]
The fourth method is a method in which iron ions or aluminum ions are dissolved in an organic waste water as a flocculant and precipitated as iron phosphate or aluminum phosphate (see Patent Document 1).
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-185086
[0008]
[Problems to be solved by the invention]
Here, the insoluble phosphorus compound obtained in the first method and the second method as described above is in a state of being mixed with sludge contained in organic wastewater, and the phosphorus compound is used as a fertilizer. When used, it is possible to reuse the phosphorus compound without separating it from the sludge. However, when reused for purposes other than fertilizer, it was necessary to repeat the refining operation in order to remove organic matter.
[0009]
On the other hand, phosphorus compounds are separated from sludge when they cannot be used as fertilizers, such as the phosphorus compounds recovered by the third and fourth methods, or when reused for purposes other than fertilizers. It needs to be recovered. In this case, after the phosphorus compound is dissolved with an acid in a state in which sludge is contained, a compound that forms a salt is added, and the phosphate is reprecipitated by adjusting the pH, so that it can be used as a fertilizer. The compound or the phosphorus compound with high purity was recovered.
[0010]
However, in the above method, the sludge is dissolved at the same time as the phosphorus compound, so that there is a problem that organic substances in the sludge are mixed into the phosphate during the reprecipitation treatment. The contaminated organic matter can be removed by repeating re-dissolution with acid and purification by phosphate re-formation. However, the operation becomes complicated and the processing time is prolonged and the cost is increased. was there. Furthermore, since the organic waste water after separating the phosphate contains nitrogen compounds and organic substances, a special treatment for draining was necessary.
[0011]
Therefore, the present invention has been made to solve the conventional technical problems, and the phosphorus compound contained in the organic wastewater can be isolated in a suitable state to improve the reuse value. Another object of the present invention is to provide a method for separating phosphorus in organic wastewater that can suitably treat organic matter and nitrogen compounds in the organic wastewater.
[0012]
[Means for Solving the Problems]
That is, in separating phosphorus from an organic wastewater containing at least a nitrogen compound and a phosphorus compound, a COD or BOD reduction treatment step for treating an organic substance in the organic wastewater, and after completion of the COD or BOD reduction treatment step, the electrochemical Treatment step for treating nitrogen compounds in organic wastewater by a general technique, a phosphorus treatment step for treating phosphorus compounds in organic wastewater by an electrochemical technique after completion of the nitrogen treatment step, and the phosphorus treatment step And a phosphorus compound separation treatment step for separating the phosphorus compound in the organic waste water.
[0013]
The method for separating phosphorus in organic wastewater according to claim 2 is the above invention, wherein one electrode used for the electrochemical method in the nitrogen treatment step and the phosphorus treatment step is hypohalous acid, ozone, or activity. A conductor capable of generating oxygen is used, and the other electrode is a conductor containing iron. In the nitrogen treatment step, one electrode is an anode, the other electrode is a cathode, and one electrode is used in a phosphorus treatment step. The cathode and the other electrode are anodes.
[0014]
In the method for separating phosphorus in organic wastewater according to the invention of claim 3, in each of the above inventions, the phosphorus compound separation treatment step is constituted by a microporous thin film, and the organic wastewater is filtered through the microporous thin film. This is characterized in that it is carried out by a filtration means for separating phosphorus compounds in organic wastewater.
[0015]
In the method for separating phosphorus in organic wastewater according to the invention of claim 4, in each of the above inventions, the COD or BOD reduction treatment step is performed by partially immersing a pair of electrodes in the organic wastewater, It includes an organic substance decomposition treatment step for decomposing organic substances in wastewater.
[0016]
The method for separating phosphorus from organic waste water according to the invention of claim 5 is characterized in that, in the above invention, the COD or BOD reduction treatment step includes a biological treatment step before the organic matter decomposition treatment step.
[0017]
The method for separating phosphorus in organic wastewater according to claim 6 is characterized in that, in each of the above inventions, the COD or BOD reduction treatment step substantially completely decomposes organic matter in the organic wastewater.
[0018]
According to the method for separating phosphorus from the organic wastewater of the present invention, the COD or BOD reduction treatment step for treating the organic matter in the organic wastewater, and after completion of the COD or BOD reduction treatment step, the organic method is performed by an electrochemical method. A nitrogen treatment step for treating a nitrogen compound in an organic wastewater, a phosphorus treatment step for treating a phosphorus compound in an organic wastewater by an electrochemical method after the completion of the nitrogen treatment step, and after the completion of the phosphorus treatment step, A phosphorus compound separation treatment step for separating the phosphorus compound in the organic wastewater, and after reducing the COD or BOD of the organic matter contained in the organic wastewater once in the COD or BOD reduction treatment step, the nitrogen Nitrogen compounds contained in organic wastewater are treated in the treatment step, and phosphorus compounds contained in organic wastewater are treated in the phosphorus treatment step. So that it is able to. Thereafter, the phosphorus compound in the organic waste water can be separated in the phosphorus compound separation treatment step.
[0019]
Here, in the organic waste water in the phosphorus compound separation treatment step, since the organic matter is reduced in the preceding COD or BOD reduction treatment step, the phosphorus compound is separated in a state in which the organic matter is taken into the phosphorus compound. Inconvenience can be remarkably suppressed.
[0020]
Thereby, the possibility that, for example, toxic organic substances are taken into the separated phosphorus compound can be significantly reduced, and the phosphorus compound can be reused in a suitable state as a fertilizer.
[0021]
In the present invention, as in the invention of claim 2, one of the electrodes used in the electrochemical method in the nitrogen treatment step and the phosphorus treatment step can generate hypohalous acid, ozone, or active oxygen. And the other electrode is a conductor containing iron, and in the nitrogen treatment step, one electrode is an anode and the other electrode is a cathode. Nitrogen compounds in organic wastewater can be effectively treated with an oxidizing agent such as acid, ozone, or active oxygen.
[0022]
In addition, since one electrode serves as a cathode and the other electrode serves as an anode in the phosphorus treatment step, iron (II) ions are eluted from the other electrode serving as the anode into the organic waste water, The iron (III) ion oxidized to the iron (III) ion in the waste water can be chemically reacted with the phosphate ion as the phosphorus compound in the organic waste water so that it can be precipitated as iron phosphate. become.
[0023]
As a result, the phosphorus compound can be separated as iron phosphate in the phosphorus compound separation processing step.
[0024]
Further, according to the invention of claim 3, in addition to the above inventions, the phosphorus compound separation treatment step is constituted by a microporous thin film, and by filtering organic waste water through the microporous thin film, Since it is performed by a filtration means for separating the phosphorus compound in the organic wastewater, the phosphorus compound can be separated from the organic wastewater.
[0025]
According to the invention of claim 4, in each of the above-mentioned inventions, the COD or BOD reduction treatment step comprises immersing part of the pair of electrodes in the organic waste water and decomposing the organic matter in the organic waste water by an electrochemical method. Therefore, the organic matter in the organic waste water can be effectively converted into nitrate nitrogen. Thereby, it becomes possible to improve the treatment efficiency of the nitrogen compound in the subsequent nitrogen treatment step.
[0026]
Further, the COD or BOD reduction treatment step as in the invention of claim 5 includes a biological treatment step before the organic matter decomposition treatment step, so that the organic matter in the organic wastewater is once decomposed and removed in the biological treatment step. After that, the organic matter decomposition processing step can be performed, and the COD or BOD reduction processing step can be more efficiently performed.
[0027]
According to the invention of claim 6, in each of the above inventions, the COD or BOD reduction treatment step substantially completely decomposes the organic matter in the organic wastewater, so that the phosphorus compound separated in the subsequent phosphorus compound separation treatment step It becomes possible to avoid the inconvenience of containing an organic substance therein, and it can be reused as a phosphorus compound having a high purity.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing an outline of a treatment system 1 for realizing the method for separating phosphorus in organic wastewater of the present invention. FIG. 2 shows a biological treatment tank 12, an organic matter decomposition treatment apparatus 2, nitrogen and phosphorus treatment. 3 is an explanatory diagram showing an outline of the device 3. FIG. The treatment system 1 in this embodiment has an organic matter decomposition treatment device 2 as COD or BOD reduction treatment means, nitrogen and phosphorus treatment device 3 as nitrogen and phosphorus treatment means, and a phosphorus compound separation treatment device 15. Yes. In addition, a biological treatment tank 12 that constitutes a COD or BOD reduction treatment means together with the organic matter decomposition treatment apparatus 2 is provided in the preceding stage of the organic matter decomposition treatment apparatus 2.
[0029]
The biological treatment tank 12 in the present embodiment includes an aerobic tank (not shown), and the aerobic tank holds activated sludge and the like that can decompose and remove organic substances.
[0030]
The organic matter decomposition treatment apparatus 2 is opposed to a treatment tank 5 constituting a treatment chamber 4 having a drainage inlet and an outlet (not shown) inside, so that at least a part is immersed in the water to be treated in the treatment chamber 4. A pair of electrodes 6 and 7, a power source (not shown) for energizing the electrodes 6 and 7, a control device for controlling the power source, and the like. The treatment tank 5 may be provided with a stirring means for stirring the inside.
[0031]
The electrodes 6 and 7 are made of a noble metal electrode such as platinum (Pt) or a mixture of platinum and iridium (Ir), or an insoluble conductor covering these. In this embodiment, a platinum / iridium electrode is used.
[0032]
On the other hand, the nitrogen and phosphorus treatment apparatus 3 in the present embodiment includes a nitrogen and phosphorus treatment tank 9 that constitutes a treatment chamber 8 having an inlet and an outlet of water to be treated (not shown) inside, and a target in the treatment chamber 8. From a pair of electrodes 10 and 11 disposed so as to be at least partially immersed in the treated water, a power source (not shown) for energizing the electrodes 10 and 11, a control device for controlling the power source, and the like It is configured. The treatment tank 9 may be provided with a stirring means for stirring the inside.
[0033]
The electrode 10 (one electrode) is a noble metal electrode such as platinum (Pt) or a mixture of platinum and iridium (Ir) as a conductor capable of generating hypohalous acid, ozone, or active oxygen. Or an insoluble conductor covering them. On the other hand, the electrode 11 (the other electrode) is made of iron (Fe) or a conductor coated with iron (a conductor containing iron).
[0034]
In this embodiment, one of the electrodes is platinum or a platinum / iridium noble metal electrode as a conductor capable of generating hypohalous acid, ozone, or active oxygen, or an insoluble electrode coated with these. Although a conductor is used, other than this, a ceramic-based conductor electrode, a carbon-based conductor electrode, a stainless steel electrode, or a conductor covering these may be used.
[0035]
Next, the phosphorus compound separation processing apparatus 15 will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic cross-sectional view of the phosphorus compound separation processing apparatus 15, and FIG. 4 is a perspective view of the microporous thin film 24. The phosphorus compound separation treatment device 15 includes a filtration treatment tank 22 that stores water to be treated, a plurality of microporous thin films 24 disposed in the filtration treatment tank 22, and a wastewater separated by the microporous thin film 24. A suction pump (not shown) for sucking the air and a blower 28 provided in the lower part of the filtration treatment tank 22 are provided.
[0036]
As shown in FIG. 4, the microporous thin film 24 includes film bodies 30 and 30 that form front and rear surfaces, and a frame body 33 that surrounds the periphery of the film bodies 30 and 30. Spacers 32 and 32 and a support body 34 are formed inside the film bodies 30 and 30. In addition, a water collection outlet 36 is formed at the upper part of the frame 33 to communicate with the membranes 30 and 30 and to be connected to the suction pump.
[0037]
Here, the film bodies 30 and 30 are film members in which micropores having a predetermined diameter or less are formed, and allow only moisture to pass through without passing through the fine particles contained in the water to be treated. Thereby, fine particles (iron phosphate in this embodiment) in the water to be treated are separated by the film body 30, and only the water sucked into the film body 30 is formed on the microporous thin film 24. It is discharged to the outside through the outlet 36.
[0038]
The blower 28 provided at the lower portion of the filtration treatment tank 22 supplies air bubbles into the filtration treatment tank 22. The bubbles form a swirling flow, and the fine particles adhering to the surface of the microporous thin film 24 are aerated and washed. As a result, only the water in the water to be treated is sucked and passed through the film body 30 while aeration cleaning is performed on the microporous thin film 24, so that stable drainage is performed while suppressing the blocking of the micropores in the film body 30. Can do.
[0039]
With the above configuration, in this embodiment, organic waste water, for example, waste water from a pig farmer is treated as treated water, and phosphorus compounds in the treated water are separated. It is assumed that the water to be treated contains a large amount of organic matter having a high COD (chemical oxygen demand). First, the water to be treated is stored in the biological treatment tank 12, and the organic matter (organic polymer) contained in the water to be treated is once decomposed (biological treatment step).
[0040]
Thereafter, the water to be treated after being treated in the biological treatment tank 12 is stored in the treatment chamber 4 in the organic matter decomposition treatment apparatus 2, the power is turned on by the control device, and a positive potential is applied to the electrode 6. A negative potential is applied to the organic substance (organic substance decomposition treatment step as a COD or BOD reduction treatment step; left middle of FIG. 2). Thereby, the electrode 6 becomes an anode and the electrode 7 becomes a cathode.
[0041]
By applying such a potential, on the electrode 6 side constituting the anode, organic substances contained in the water to be treated are decomposed into nitrate ions as nitrate nitrogen, ammonia or ammonium ions as ammonia nitrogen, or carbon dioxide and water. (Reaction A). Reaction A is shown below.
Reaction A Organic matter → NO_Three ^-+ NH_Three+ CO₂+ H₂O
[0042]
On the platinum / iridium electrode 6 side constituting the anode, chloride ions contained in the water to be treated release electrons to generate chlorine (reaction B). And this chlorine melt | dissolves in water and produces | generates hypochlorous acid as hypohalogenous acid (reaction C). Further, the produced hypochlorous acid reacts with ammonia (ammonium ions) produced in the water to be treated in the above-mentioned reaction A, undergoes a plurality of chemical changes, and is converted into nitrogen gas (reaction D). Hereinafter, Reaction B to Reaction D are shown. At this time, ozone or active oxygen is simultaneously generated on the electrode.

[0043]
Thereby, while removing ammonia or ammonium ion, the organic substance in organic wastewater can be efficiently converted into nitrate nitrogen.
[0044]
Further, ammonia (ammonium ions) in the water to be treated reacts with ozone generated on the electrode 10 side constituting the anode or active oxygen as shown in the reaction E, and this is also denitrified into nitrogen gas.
Reaction E 2NH_Three(Aq) +3 (O) → N₂↑ + 3H₂O
[0045]
As a result, ammonia nitrogen can be removed from nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen converted from organic matter in the organic matter decomposition treatment step, and residual organic matter can be treated up to nitrate nitrogen. . In this case, since the water to be treated is treated in the biological treatment step before the organic matter decomposition treatment step, the decomposition efficiency of the organic matter is improved, and the organic matter in the treated water is effectively decomposed. It becomes possible to process. In this embodiment, in order to separate a high-purity phosphorus compound from the water to be treated, it is preferable to substantially completely decompose the organic matter in the water to be treated in the organic matter decomposition treatment step.
[0046]
In the present embodiment, the electrodes 6 and 7 provided in the organic substance decomposition treatment apparatus 2 are both composed of platinum / iridium electrodes. Therefore, the electrodes 6 and 7 are attached to the electrodes 6 and 7 every elapse of a predetermined time, for example, 30 minutes. It is also possible to switch the applied polarity.
[0047]
As a result, organic matter and scale (CaCO) adhered to the surface of the electrode 7 or 6 constituting the cathode._Three, Mg (OH)₂Etc.) is switched off from the surface when the polarity of each electrode 6, 7 is switched and the electrode 7 or 6 becomes an anode. Thereby, the electrolytic performance of the electrode 7 or 6 can be maintained high.
[0048]
After the completion of the organic substance decomposition treatment (organic substance decomposition treatment step), the water to be treated in the organic substance decomposition treatment tank 5 is conveyed into the treatment tank 9 of the nitrogen and phosphorus treatment apparatus 3, and the organic substance is introduced into the treatment tank 9. The treated water that has been decomposed is stored. Then, the power is turned on by the control device, and first, a positive potential is applied to the electrode 10 and a negative potential is applied to the electrode 11 (nitrogen treatment step, middle right in FIG. 2). Thereby, the electrode 10 becomes an anode and the electrode 11 becomes a cathode.
[0049]
By applying such a potential, electrons generated on the electrode 10 side constituting the anode are supplied to the electrode 11 side constituting the cathode, and nitrate ions as nitrate nitrogen contained in the water to be treated are reduced to nitrite ions. (Reaction F). Further, nitrate nitrogen reduced to nitrite ions is supplied with electrons on the electrode 11 side constituting the cathode, and is reduced to ammonia (ammonium ions) (reaction G). Below, reaction F and reaction G are shown.
Reaction F NO_Three ^-+ H₂O + 2e^-→ NO₂ ^-+ 2OH^-
Reaction G NO₂ ^-+ 5H₂O + 6e^-→ NH_Three(Aq) + 7OH^-
[0050]
On the other hand, on the platinum / iridium electrode 10 side constituting the anode, chloride ions contained in the water to be treated emit electrons to generate chlorine. And this chlorine melt | dissolves in water and produces | generates hypochlorous acid. At this time, ozone or active oxygen is simultaneously generated on the electrode.
[0051]
Here, when the concentration of chloride ions contained in the water to be treated is low, the water to be treated contains, for example, chloride ions, halide ions such as iodide ions and bromide ions, and these halide ions. Compounds such as potassium chloride and sodium chloride may be added. That is, the chloride ion of the potassium chloride of to-be-processed water shall be 10 ppm or more and 40000 ppm or less, for example.
[0052]
Such chloride ions originally contained in the water to be treated and potassium chloride added as described above are oxidized at the electrode 10 constituting the anode to generate chlorine (reaction B, shown in the case of potassium chloride), The produced chlorine reacts with water in the water to be treated to produce hypochlorous acid (reaction C). The produced hypochlorous acid reacts with ammonia (ammonium ions) produced in the water to be treated in the above-mentioned reaction G, undergoes a plurality of chemical changes, and is then converted into nitrogen gas (the reaction D). ).
[0053]
In addition, ammonia (ammonium ions) in the water to be treated reacts with ozone generated on the electrode 10 side constituting the anode or active oxygen as shown in the reaction E, and is denitrified into nitrogen gas by this reaction. .
[0054]
Thereby, it becomes possible to easily treat the nitrogen compound treated to nitrate nitrogen in the organic substance decomposition treatment step.
[0055]
After completion of the nitrogen compound treatment (nitrogen treatment step) as described above, the control device switches the polarity of the potential applied to each of the electrodes 10 and 11 (the lower stage of FIG. 2; the phosphorus treatment step. The above nitrogen treatment reaction continues in water). Thus, the electrode 10 constitutes a cathode and the electrode 11 constitutes an anode. As a result, the water to be treated is subjected to electrolytic treatment as an electrochemical method, and the electrode 11 constituting the anode is composed of a conductor containing iron as described above. ) Ions elute into the treated water and are oxidized to iron (III) ions in the treated water.
[0056]
The produced iron (III) ions coagulate and precipitate with phosphate ions in the water to be treated by a dephosphorylation reaction as shown in Reaction H to produce iron phosphate that is hardly soluble in water.
Reaction H Fe³⁺+ PO_Four ^3-→ FePO_Four↓
Thereby, the phosphate ion as a phosphorus compound contained in to-be-treated water can be subjected to precipitation treatment as iron phosphate.
[0057]
In addition, in this case, a part of iron (III) ions eluted in the state of iron (II) ions in the water to be treated for supply of electrons and oxidized on the electrodes or in the water to be treated constitute a cathode. On the electrode 10 side, electrons are supplied again and reduced to iron (II) ions to reduce nitric acid or be oxidized by oxygen.
[0058]
In addition, about the technique which reduces the nitrate ion contained in a to-be-processed water to an ammonium ion by electrolyzing the to-be-processed water containing iron (II) ion, it has already been 3 from March 16, 1999. It is disclosed in “Development of Inorganic Nitrogen Compound Treatment Technology Using Electrochemical Reaction” in the Annual Meeting of the Japan Society on Water Environment, which was distributed at the 33rd Annual Meeting of the Japan Society on Water Environment held on May 18.
[0059]
In this embodiment, the electrochemical treatment of the nitrogen treatment step and the phosphorus treatment step is performed by switching the polarity using the common electrodes 10 and 11, but in addition to this, both steps are performed. It is also possible to use respective electrodes for executing the above. For example, in the nitrogen treatment step, one electrode and the other electrode are each composed of a conductor capable of generating hypohalous acid, ozone, or active oxygen, and in the phosphorus treatment step, the above-described embodiment is used. One electrode is composed of a conductor capable of generating hypohalous acid, ozone, or active oxygen, and the other electrode is iron (Fe) or a conductor coated with iron. It may be configured by. Thereby, the treatment efficiency of the water to be treated in the nitrogen treatment step can be improved.
[0060]
After the treatment of the phosphorus compound as described above (phosphorus treatment step), the nitrogen and the water to be treated and the precipitate in the treatment tank 9 of the phosphorus treatment apparatus 3 are transported to the filtration treatment tank 22, and in the filtration treatment tank 22. The treated water and the precipitate after nitrogen / phosphorus treatment are stored. In this embodiment, the treatment tank 9 and the filtration treatment tank 22 of the nitrogen / phosphorus treatment apparatus 3 are configured as separate tanks, but may be configured as the same tank.
[0061]
When the blower 28 and the suction pump are operated in the filtration tank 22 by a control device (not shown), only the water in the water to be treated in the filtration tank 22 is filtered into the film body 30 of the microporous thin film 24. At this time, iron phosphate that is sparingly soluble in water contained in the water to be treated adheres to the surface of the film body 30.
[0062]
The water to be treated sucked into the membrane 30 of the microporous thin film 24 is separated from the iron phosphate by passing through the membrane 30, and then to the water collection outlet 36 through the spacer 32 and the support 34. It reaches and is discharged to the outside by the suction pump.
[0063]
On the other hand, the iron phosphate adhering to the surface of the microporous thin film 24 is aerated and cleaned by bubbles generated from the blower 28, peeled off from the microporous thin film 24, floats in the filtration treatment tank 22, and enters the filtration treatment tank 22. Sink at the bottom. By collecting the deposited iron phosphate, a highly pure phosphorus compound can be easily obtained.
[0064]
As described above in detail, in this embodiment, the water to be treated is treated in the nitrogen treatment step after the COD or BOD of the organic matter contained in the water to be treated is once reduced in the COD or BOD reduction treatment step. Since nitrogen compounds contained in water are treated, and phosphorus compounds contained in water to be treated are precipitated in the phosphorus treatment step, phosphorus compounds in the water to be treated can be easily separated in the phosphorus compound separation treatment step. become.
[0065]
In particular, in the water to be treated in the phosphorus compound separation treatment step, organic matter is reduced in the preceding COD or BOD reduction treatment step, so that the phosphorus compound is separated in a state where the organic matter is taken into the phosphorus compound. It can be significantly suppressed.
[0066]
Thereby, the possibility that, for example, toxic organic substances are taken into the separated phosphorus compound can be significantly reduced, and the phosphorus compound can be reused in a suitable state as a fertilizer.
[0067]
In addition, when the COD or BOD of the organic matter contained in the water to be treated is almost completely decomposed in the COD or BOD reduction treatment step, the phosphorus compound (iron phosphate) precipitated in the phosphorus treatment step is an organic matter. Therefore, it is possible to avoid the disadvantage that organic substances are contained in the phosphorus compound (iron phosphate) separated in the phosphorus compound separation treatment step. It can be used. Thereby, the reuse value of the phosphorus compound obtained from organic wastewater can be improved.
[0068]
In addition, since the phosphorus compound collect | recovered in a present Example is iron phosphate, when using, for example as a fertilizer of a leguminous plant, it becomes possible to use it without performing a special process after that. When used as a fertilizer for other plants, it is necessary to remove iron in order to improve the absorbability of phosphorus. In that case, for example, it is preferable to use the ferric fertilizer in a state where the iron phosphate is dissolved using an organic acid such as malic acid or citric acid and the iron is removed.
[0069]
【The invention's effect】
As described above in detail, according to the present invention, a COD or BOD reduction treatment step for treating organic substances in organic wastewater, and a nitrogen compound in the organic wastewater by an electrochemical method after completion of the COD or BOD reduction treatment step. A nitrogen treatment step for treating the phosphorus compound in the organic wastewater after the completion of the nitrogen treatment step, and a phosphorus treatment step for treating the phosphorus compound in the organic wastewater by an electrochemical method. And a phosphorus compound separation treatment step for separating the compound, so that once the COD or BOD of the organic matter contained in the organic wastewater is reduced in the COD or BOD reduction treatment step, the organic treatment is performed in the nitrogen treatment step. Nitrogen compounds contained in wastewater can be treated, and phosphorus compounds contained in organic wastewater can be treated in the phosphorus treatment step. To become. Thereafter, the phosphorus compound in the organic waste water can be separated in the phosphorus compound separation treatment step.
[0070]
Here, in the organic waste water in the phosphorus compound separation treatment step, since the organic matter is reduced in the preceding COD or BOD reduction treatment step, the phosphorus compound is separated in a state in which the organic matter is taken into the phosphorus compound. Inconvenience can be remarkably suppressed.
[0071]
Thereby, the possibility that, for example, toxic organic substances are taken into the separated phosphorus compound can be significantly reduced, and the phosphorus compound can be reused in a suitable state as a fertilizer.
[0072]
In the present invention, as in the invention of claim 2, one of the electrodes used in the electrochemical method in the nitrogen treatment step and the phosphorus treatment step can generate hypohalous acid, ozone, or active oxygen. And the other electrode is a conductor containing iron, and in the nitrogen treatment step, one electrode is an anode and the other electrode is a cathode. Nitrogen compounds in organic wastewater can be effectively treated with an oxidizing agent such as acid, ozone, or active oxygen.
[0073]
In addition, since one electrode serves as a cathode and the other electrode serves as an anode in the phosphorus treatment step, iron (II) ions are eluted from the other electrode serving as the anode into the organic waste water, The iron (III) ion oxidized to the iron (III) ion in the waste water can be chemically reacted with the phosphate ion as the phosphorus compound in the organic waste water so that it can be precipitated as iron phosphate. become.
[0074]
As a result, the phosphorus compound can be separated as iron phosphate in the phosphorus compound separation processing step.
[0075]
Further, according to the invention of claim 3, in addition to the above inventions, the phosphorus compound separation treatment step is constituted by a microporous thin film, and by filtering organic waste water through the microporous thin film, Since it is performed by a filtration means for separating the phosphorus compound in the organic wastewater, the phosphorus compound can be separated from the organic wastewater.
[0076]
According to the invention of claim 4, in each of the above-mentioned inventions, the COD or BOD reduction treatment step comprises immersing part of the pair of electrodes in the organic waste water and decomposing the organic matter in the organic waste water by an electrochemical method. Therefore, the organic matter in the organic waste water can be effectively converted into nitrate nitrogen. Thereby, it becomes possible to improve the treatment efficiency of the nitrogen compound in the subsequent nitrogen treatment step.
[0077]
Further, the COD or BOD reduction treatment step as in the invention of claim 5 includes a biological treatment step before the organic matter decomposition treatment step, so that the organic matter in the organic wastewater is once decomposed and removed in the biological treatment step. After that, the organic matter decomposition processing step can be performed, and the COD or BOD reduction processing step can be more efficiently performed.
[0078]
According to the invention of claim 6, in each of the above inventions, the COD or BOD reduction treatment step substantially completely decomposes the organic matter in the organic wastewater, so that the phosphorus compound separated in the subsequent phosphorus compound separation treatment step It becomes possible to avoid the inconvenience of containing an organic substance therein, and it can be reused as a phosphorus compound having a high purity.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an outline of a treatment system for realizing a method for separating phosphorus in organic wastewater of the present invention.
FIG. 2 is an explanatory view showing an outline of a biological treatment tank, an organic matter decomposition treatment apparatus, and a nitrogen and phosphorus treatment apparatus.
FIG. 3 is a schematic sectional view of a phosphorus compound separation treatment apparatus.
FIG. 4 is a perspective view of a microporous thin film.
[Explanation of symbols]
1 Processing system
2 Organic matter decomposition equipment
3 Nitrogen and phosphorus treatment equipment
4 treatment room
5 Organic matter decomposition treatment tank
6, 7, 10, 11 electrodes
8 treatment room
9 Nitrogen and phosphorus treatment tank
12 Biological treatment tank
15 Filtration processing equipment
22 Filtration tank
24 Microporous thin film
30 Membrane

Claims (6)

A method for separating phosphorus from organic waste water containing at least a nitrogen compound and a phosphorus compound,
A COD or BOD reduction treatment step for treating organic matter in the organic wastewater; and a nitrogen treatment step for treating a nitrogen compound in the organic wastewater by an electrochemical method after the completion of the COD or BOD reduction treatment step;
After the completion of the nitrogen treatment step, a phosphorus treatment step of treating the phosphorus compound in the organic wastewater by an electrochemical method;
A method for separating phosphorus in organic wastewater, comprising: a phosphorus compound separation treatment step for separating a phosphorus compound in the organic wastewater after completion of the phosphorus treatment step. One electrode used for the electrochemical method in the nitrogen treatment step and the phosphorus treatment step is a conductor capable of generating hypohalous acid, ozone, or active oxygen, and the other electrode contains iron. As a conductor,
2. The organic of claim 1, wherein said one electrode is an anode and said other electrode is a cathode in said nitrogen treatment step, and said one electrode is a cathode and said other electrode is an anode in said phosphorus treatment step. To separate phosphorus from wastewater. The phosphorus compound separation treatment step is constituted by a microporous thin film, and is performed by a filtration treatment means for separating the phosphorus compound in the organic waste water by filtering the organic waste water through the microporous thin film. The method for separating phosphorus in an organic wastewater according to claim 1 or 2, wherein: The COD or BOD reduction treatment step includes an organic matter decomposition treatment step of partially immersing a pair of electrodes in the organic wastewater, and decomposing the organic matter in the organic wastewater by an electrochemical method. The method for separating phosphorus in an organic wastewater according to claim 1, 2 or 3. 5. The method for separating phosphorus in organic wastewater according to claim 4, wherein the COD or BOD reduction treatment step includes a biological treatment step prior to the organic matter decomposition treatment step. The organic matter according to claim 1, 2, 3, 4, or 5, wherein the COD or BOD reduction treatment step substantially completely decomposes organic matter in the organic wastewater. Method for separating phosphorus in wastewater.

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