JP3565304B2

JP3565304B2 - Organic wastewater treatment method and equipment

Info

Publication number: JP3565304B2
Application number: JP15618797A
Authority: JP
Inventors: 昭渡辺; 慶泉蘇; 信和木幡; 健治島
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 1996-07-09
Filing date: 1997-05-30
Publication date: 2004-09-15
Anticipated expiration: 2017-05-30
Also published as: JPH1076299A

Description

【０００１】
【発明の属する技術分野】
本発明は、有機性汚水の処理方法に係り、特に、有機性汚水を好気性生物処理して得られる余剰汚泥を可溶化する処理方法と装置に関する。
【０００２】
【従来の技術】
従来、有機性汚水の好気性生物処理（活性汚泥法、生物学的硝化脱窒素法など）の最大の問題点は水質を浄化する工程に存在するのではなく、むしろ汚泥処理工程にある。
すなわち、好気性生物処理方法は、余剰活性汚泥の発生量が非常に多い点に最大の問題点がある。余剰活性汚泥は、現在脱水後埋立てあるいは焼却処分されているが、多大の経費と設備を必要としていた。
従来の活性汚泥法の余剰汚泥の発生量は、数多くの実験あるいは実績により、除去ＢＯＤ当り、０．６〜０．８（ｋｇＳＳ／ｋｇＢＯＤ）程度となることが良く知られている。
【０００３】
その上、余剰汚泥は、質的にも難脱水性であるため、益々汚泥処理が困難になっている。
このような、余剰汚泥を減少するために、従来余剰汚泥の可溶化処理方法として、アルカリ剤を添加して処理する方法（特開平２−２２７１９０号公報参照）、一方にアルカリ剤、片方に酸を添加して処理する方法（特開平２−２９３０９５号公報）等が知られていたが、これらの処理方法でも余剰汚泥はある程度減少するものの、より以上の減容化方法が望まれていた。
【０００４】
【発明が解決しようとする課題】
本発明は、上記従来技術に鑑み、簡単な処理手段により余剰汚泥のほとんど発生しない、有機性汚水の好気性生物処理方法と装置を提供することを課題とする。
【０００５】
【課題を解決するための手段】
上記課題を解決するために、本発明では、有機性汚水を好気性生物処理した後、得られる汚泥の一部を可溶化処理して前記好気性生物処理工程に戻して処理する方法において、前記可溶化処理が酸性酸化剤を用いる酸性酸化処理工程とアルカリ剤を用いるアルカリ処理工程から成り、前記酸性酸化剤とアルカリ剤が、塩水を隔膜電解して得られた酸性酸化水とアルカリ水であることとしたものである。
また、前記酸性酸化処理工程とアルカリ処理工程が、並列又は直列に設けられ、それぞれ複数の工程からなり、該複数の工程から成る酸性酸化処理工程及びアルカリ処理工程では、該工程の前段の工程に酸性酸化剤又はアルカリ剤を全量導入するとともに、被処理汚泥を各段の工程に分配して導入するのがよい。
【０００６】
また、前記可溶化処理した汚泥は、好気性生物処理工程に戻す前に前曝気工程を設けて曝気処理して残留塩素を揮発除去するのが良く、さらに、該汚泥の一部は、再度可溶化処理する工程に戻して処理することにより、より分解性は向上する。
また、本発明では、有機性汚水を好気性生物処理する生物処理槽と、生物処理した処理液を固液分離する固液分離装置と、固液分離した汚泥の一部を可溶化処理する可液化処理手段と、可溶化処理した処理液を前記好気性生物処理槽に戻す流路とを有する有機性汚水の処理装置において、前記可溶化処理手段が、酸性酸化剤を用いる酸性酸化処理槽及びアルカリ剤を用いるアルカリ処理槽と、該酸性酸化処理槽及びアルカリ処理槽に酸性酸化剤とアルカリ剤を供給する塩水の隔膜電解装置とから成ることを特徴とする有機性汚水の処理装置としたものである。
なお、可溶化処理で酸性酸化処理工程及びアルカリ処理工程で処理した汚泥は、これらを混合することにより中性に戻すが、万一ｐＨが中性域を外れた場合は、酸性酸化水又はアルカリ水を用いて中性に戻すのが良い。
【０００７】
【発明の実施の形態】
次に図面を用いて本発明を詳細に説明する。
図１に本発明の処理方法の汚泥減容化プロセスのフローの一例を示す。
図１においては、有機性汚水１２を、好気性生物処理槽１で処理し、沈殿槽２で固液分離して処理水１３と汚泥１４、１５を得る排水処理工程で処理し、発生した汚泥の一部を返送汚泥１４として生物処理槽１に循環すると共に、他部１５を可溶化工程３に導入して、汚泥を可溶化及び分解処理を行った後、排水処理工程の生物処理槽１に返送１８して、溶解性有機物及び汚泥分の生物分解を行っている。
可溶化工程３に導入された汚泥１５は、並列で複数（２槽づつ）設けられたアルカリ処理工程５、５′と酸化処理工程４、４′にそれぞれ導入され、海水又は塩素イオンを含む各種の塩水を隔膜電解して得られたアルカリ水２１及び酸性酸化水２０と接触させることにより可溶化及び酸化分解処理を行っている。
【０００８】
前記可溶化工程３では、アルカリ処理工程と酸化処理工程が並列で複数設置されているが、図２に部分工程図として示すように、アルカリ処理工程５、５′と酸化処理工程４を直列に設置することができる。この場合、酸性酸化水からの塩素臭はアルカリ汚泥に吸収されて脱臭され、また、汚泥はアルカリ処理と酸化処理の両方の処理を受けるので分解性が向上する。
塩水の隔膜電解は、隔膜１１によって陽極９を有する陽極室７と陰極８を有する陰極室１０によって仕切られた隔膜電解装置６を用いて行い、該装置６の陽極室７と陰極室８に塩水１９を導入する。陽極室７では、陽極でＨ^＋が生成し、酸性になると共に、塩水中のＣｌ⁻より塩素系酸化剤（ＨＣｌＯ、Ｃｌ_２、Ｃｌ・等）が発生し、酸性酸化水２０を得、陰極室８では、陰極でＯＨ⁻が生成しアルカリ性になり、アルカリ水２１を得て、酸性酸化水２０を酸化槽４に、アルカリ水２１をアルカリ槽５にそれぞれ導入して可溶化処理に用いる。
また、アルカリ処理工程と酸化処理工程はそれぞれ処理槽を２段に設け、それぞれに導入された汚泥１６、１７の一部は、第２アルカリ槽５′と第２酸化槽４′にそれぞれ分流して導入する。
【０００９】
次に、これらの槽の作用を説明する。
まず、第１アルカリ槽は、隔膜電解により生成したアルカリを汚泥に反応させ、強アルカリ条件下で汚泥菌体の破壊及び細胞内液の溶出による汚泥の可溶化処理を行い、第２アルカリ槽は、第１アルカリ槽からの余剰アルカリを利用して、汚泥の可溶化を進行させる。
次に、第１酸化槽は、隔膜電解により生成した酸、酸化剤を汚泥に反応させ強酸条件下で汚泥菌体の酸化分解処理を行う、第２酸化槽は、第１酸化槽からの余剰の酸、酸化剤を利用して、汚泥の酸化分解を進行させる。
なお、図１では、アルカリ処理及び酸性酸化処理を並列でそれぞれ２系列で行っているが、各々の処理は、単一槽（第１アルカリ槽と第１酸化槽のみ）でも良いし、それぞれを２槽以上の系列で行ってもよいし、直列で単一又は２槽以上で行ってもよい。
【００１０】
図３に、本発明の処理方法の別の概略フロー工程図を示す。図３では好気性生物処理槽１の前に調整槽２３を設け、可溶化工程３の後に前曝気槽２２を設けている。
図３においては、有機性汚水１２は生物処理槽１に入る前に調整槽２３に導入されて曝気処理される。また、可溶化工程３からの可溶化汚泥１８は、前曝気槽２２で曝気処理され、可溶化処理に用いた電解水中の残留塩素を揮発除去した後に、生物処理槽１に導入している。なお、前曝気槽２２の替りに、可溶化汚泥１８を調整槽２３に導入して、曝気処理して残留塩素を除去することができる。
図４に、可溶化汚泥１８の一部を、可溶化工程３に循環する概略フロー工程図を示す。このように、可溶化汚泥の一部を循環処理することにより、更に汚泥の分解性を向上することができる。
【００１１】
【実施例】
以下、本発明を実施例により具体的に説明する。
実施例１
図１の処理フローに示した実験装置（Ｒｕｎ１）と、同フローから可溶化工程を除いた実験装置（Ｒｕｎ２）の２系列を設けて、処理水質と汚泥発生量を比較した。Ｒｕｎ１において、可溶化工程に導入する汚泥量は余剰汚泥量の４倍量を導入し、アルカリ処理工程には、その２／３量、酸化処理工程にはその１／３量をそれぞれ導入した。また、第２アルカリ槽には、アルカリ処理工程に導入される汚泥量の１／２量、第２酸化槽には、酸化処理工程に導入される汚泥量の１／３量をそれぞれ導入した。各処理槽の滞留時間はいずれも４時間とした。本実施例では塩水として海水の１／２の塩分濃度の食塩水を用いた。また、食塩水の使用量は、余剰汚泥量と同量を電解処理槽に通水した。隔膜電解処理の条件と得られた電解水（アルカリ水、酸性酸化水）の性状を表１、２にそれぞれ示す。なお、実験はＡ食品会社の排水を原水（ｐＨ６．４、ＢＯＤ５００ｍｇ／リットル、ＣＯＤＭｎ２４０ｍｇ／リットル、ＳＳ８０ｍｇ／リットル）として、Ｒｕｎ１とＲｕｎ２の運転条件は可溶化工程を設ける以外は同条件で運転した。
【００１２】
【表１】

【表２】

【００１３】
表３に、導入汚泥と処理済汚泥の性状を示す。
【表３】

【００１４】
実験結果を表４に示す。表４から、可溶化工程を組み込んだＲｕｎ１はＲｕｎ２に比べて汚泥発生量が著しく少なく、処理水質もほとんど差はなかった。
【表４】

【００１５】
実施例２
図２の処理フロー、即ち、アルカリ槽及び酸化槽を直列に設置して可溶化処理を行う実験装置を設けて処理実験を行った。
可溶化工程に導入する汚泥量は余剰汚泥量の３倍量を導入し、第１アルカリ槽には、その２／３量（対余剰汚泥量の２倍）、第２アルカリ槽にはその１／３量をそれぞれ導入した。また、実施例１と同じく、各処理槽の滞留時間はいずれも４時間とし、使用する塩水も海水の１／２の塩分濃度の食塩水を用い、実施例１と同様に処理した。
表５に直列方式により処理した導入汚泥と処理済汚泥の性状を示す。
【表５】

【００１６】
連続実験結果を表６に示す。
【表６】

直列方式によると、アルカリ処理と酸化処理を直列に行うことで汚泥の分解性アップし、酸化槽ｐＨは中性となる。また、アルカリ汚泥に酸性酸化水を添加することにより塩素臭をなくすとともに、臭気対策用の付帯設備を低減できる等の利点がある。
【００１７】
【発明の効果】
本発明によれば、酸性酸化剤及びアルカリ剤を用いた処理により、余剰汚泥をほとんど分解でき、汚泥はほとんど発生せず、また、酸性酸化剤、アルカリ剤として塩水の隔膜処理から得られる酸性酸化水、アルカリ水を用いることにより、安価に容易に得ることができる。
【図面の簡単な説明】
【図１】本発明の処理方法に用いる汚泥減容化プロセスのフロー工程図。
【図２】可溶化工程の他の部分フロー工程図。
【図３】本発明の処理方法の別の概略フロー工程図。
【図４】本発明の処理方法の他の概略フロー工程図。
【符号の説明】
１：好気性生物処理槽、２：沈殿槽、３：可溶化工程、４：第１酸化槽、４′：第２酸化槽、５：第１アルカリ槽、５′：第２アルカリ槽、６：隔膜電解装置、７：陽極室、８：陰極室、９：陽極、１０：陰極、１１：隔膜、１２：有機性汚水、１３：処理水、１４：返送汚泥、１５：余剰汚泥、１６、１７：余剰汚泥の一部、１８：可溶化汚泥、１９：塩水、２０：酸性酸化水、２１：アルカリ水、２２：前曝気槽、２３：調整槽[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating organic sewage, and more particularly to a method and apparatus for solubilizing excess sludge obtained by aerobic biological treatment of organic sewage.
[0002]
[Prior art]
Conventionally, the biggest problem of the aerobic biological treatment of organic wastewater (activated sludge method, biological nitrification denitrification method, etc.) does not exist in the step of purifying water quality but rather in the sludge treatment step.
That is, the aerobic biological treatment method has the greatest problem in that the amount of surplus activated sludge generated is extremely large. Excess activated sludge is currently landfilled or incinerated after dehydration, but it requires a great deal of cost and equipment.
It is well known that the amount of surplus sludge generated by the conventional activated sludge method is about 0.6 to 0.8 (kgSS / kgBOD) per removed BOD, based on many experiments and results.
[0003]
In addition, surplus sludge is hardly dehydrated in quality, so that sludge treatment becomes more and more difficult.
In order to reduce such excess sludge, a conventional method of solubilizing excess sludge is to add an alkaline agent and treat it (see JP-A-2-227190). And the like (JP-A-2-293095) have been known. However, even with these treatment methods, excess sludge is reduced to some extent, but a further volume reduction method has been desired.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide an aerobic biological treatment method and apparatus for organic sewage, in which excess sludge is hardly generated by a simple treatment means in view of the above-mentioned conventional technology.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the present invention, after treating organic sewage with aerobic biological treatment, a method of solubilizing a part of the obtained sludge and returning to the aerobic biological treatment step for treatment, The solubilization treatment comprises an acid oxidation treatment step using an acid oxidizing agent and an alkali treatment step using an alkali agent , wherein the acid oxidizing agent and the alkaline agent are acidic oxidized water and alkaline water obtained by diaphragm electrolysis of salt water. It was decided.
Further, the acid oxidation treatment step and the alkali treatment step are provided in parallel or in series, each comprising a plurality of steps, and in the acid oxidation treatment step and the alkali treatment step composed of the plurality of steps, a step preceding the step is performed. It is preferable to introduce the entire amount of the acidic oxidizing agent or the alkaline agent, and to distribute and introduce the sludge to be treated in each step.
[0006]
Before returning to the aerobic biological treatment step, the solubilized sludge may be provided with a pre-aeration step to perform aeration treatment to volatilize and remove residual chlorine. By returning to the step of the solubilization treatment and performing the treatment, the decomposability is further improved.
Further, in the present invention, a biological treatment tank for aerobic biological treatment of organic wastewater, a solid-liquid separation device for solid-liquid separation of a biologically treated liquid, and a solubilization treatment for a part of solid-liquid separated sludge can be performed. Liquefaction treatment means, in an organic sewage treatment apparatus having a flow path for returning the treatment solution subjected to solubilization to the aerobic biological treatment tank, wherein the solubilization treatment means, an acid oxidation treatment tank using an acidic oxidizing agent, An organic sewage treatment apparatus comprising: an alkali treatment tank using an alkali agent; and a membrane electrolyzer for supplying the acidic oxidant and the alkali agent to the acid oxidation treatment tank and the alkali treatment tank. It is.
The sludge treated in the acid oxidation treatment step and the alkali treatment step in the solubilization treatment is returned to neutrality by mixing these. However, if the pH is out of the neutral range, the acid sludge is treated with acidic oxidized water or alkali. It is better to return to neutrality with water.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an example of a flow of a sludge volume reduction process of the treatment method of the present invention.
In FIG. 1, an organic wastewater 12 is treated in an aerobic biological treatment tank 1, and solid-liquid separated in a sedimentation tank 2 to be treated in a wastewater treatment step of obtaining treated water 13 and sludges 14 and 15. Is recycled to the biological treatment tank 1 as returned sludge 14, and the other part 15 is introduced into the solubilization step 3 to solubilize and decompose the sludge, and then to the biological treatment tank 1 in the wastewater treatment step. To biodegrade the soluble organic matter and sludge.
The sludge 15 introduced into the solubilization step 3 is introduced into a plurality (two tanks) of alkali treatment steps 5 and 5 ′ and oxidation treatment steps 4 and 4 ′, each of which is provided in parallel. Is brought into contact with alkaline water 21 and acidic oxidized water 20 obtained by subjecting the salt water to diaphragm electrolysis to perform solubilization and oxidative decomposition treatment.
[0008]
In the solubilization step 3, a plurality of alkali treatment steps and oxidation treatment steps are provided in parallel. However, as shown as a partial step diagram in FIG. 2, the alkali treatment steps 5 and 5 'and the oxidation treatment step 4 are connected in series. Can be installed. In this case, the chlorine odor from the acidic oxidized water is absorbed and deodorized by the alkali sludge, and the sludge is subjected to both alkali treatment and oxidation treatment, so that the decomposability is improved.
The diaphragm electrolysis of the salt water is performed by using a diaphragm electrolyzer 6 separated by an anode chamber 7 having an anode 9 by a diaphragm 11 and a cathode chamber 10 having a cathode 8, and the salt water is supplied to the anode chamber 7 and the cathode chamber 8 of the apparatus 6. 19 is introduced. In the anode chamber 7, H ⁺ is generated at the anode and becomes acidic, and a chlorine-based oxidizing agent (HClO, Cl ₂ , Cl, etc.) is generated from Cl ^{− in} the salt water to obtain an acidic oxidized water 20 and a cathode. In the chamber 8, OH ⁻ is generated at the cathode to become alkaline, and alkaline water 21 is obtained. The acidic oxidizing water 20 is introduced into the oxidizing tank 4 and the alkaline water 21 is introduced into the alkaline tank 5 for use in the solubilization treatment.
In the alkali treatment step and the oxidation treatment step, treatment tanks are respectively provided in two stages, and a part of the sludges 16 and 17 introduced into the treatment tanks are respectively divided into a second alkali tank 5 'and a second oxidation tank 4'. To introduce.
[0009]
Next, the operation of these tanks will be described.
First, the first alkaline tank reacts the sludge with the alkali generated by the membrane electrolysis, performs sludge solubilization by destruction of the sludge cells and elution of the intracellular solution under strong alkaline conditions, and the second alkaline tank The sludge is solubilized by utilizing excess alkali from the first alkali tank.
Next, the first oxidation tank reacts the acid and oxidizing agent generated by the diaphragm electrolysis with the sludge to perform oxidative decomposition treatment of the sludge cells under the strong acid condition. The second oxidation tank uses the surplus from the first oxidation tank. The oxidative decomposition of sludge is promoted using the acid and oxidizing agent.
In FIG. 1, the alkali treatment and the acid oxidation treatment are performed in two lines each in parallel. However, each treatment may be performed in a single tank (only the first alkali tank and the first oxidation tank), It may be performed in a series of two or more tanks, or may be performed in a single series or in two or more tanks in series.
[0010]
FIG. 3 shows another schematic flow chart of the processing method of the present invention. In FIG. 3, an adjustment tank 23 is provided before the aerobic biological treatment tank 1, and a pre-aeration tank 22 is provided after the solubilization step 3.
In FIG. 3, the organic sewage 12 is introduced into the adjusting tank 23 and aerated before entering the biological treatment tank 1. The solubilized sludge 18 from the solubilization step 3 is introduced into the biological treatment tank 1 after being subjected to aeration treatment in the pre-aeration tank 22 to volatilize and remove residual chlorine in the electrolytic water used for the solubilization treatment. Instead of the pre-aeration tank 22, the solubilized sludge 18 can be introduced into the adjustment tank 23 and subjected to aeration treatment to remove residual chlorine.
FIG. 4 is a schematic flowchart showing a process of circulating a part of the solubilized sludge 18 to the solubilizing step 3. In this way, by circulating a part of the solubilized sludge, the sludge decomposability can be further improved.
[0011]
【Example】
Hereinafter, the present invention will be described specifically with reference to examples.
Example 1
The experimental apparatus (Run 1) shown in the processing flow of FIG. 1 and the experimental apparatus (Run 2) in which the solubilization step was removed from the flow were provided, and the quality of treated water and the amount of generated sludge were compared. In Run 1, the amount of sludge introduced into the solubilization step was 4 times the amount of excess sludge, 2/3 of the amount was introduced into the alkali treatment step, and 1/3 thereof was introduced into the oxidation treatment step. In the second alkaline tank, １／ of the amount of sludge introduced into the alkali treatment step was introduced, and in the second oxidation tank, １／ of the amount of sludge introduced into the oxidation treatment step was introduced. The residence time in each treatment tank was 4 hours. In this embodiment, a salt solution having a salt concentration of 1/2 of seawater was used as the salt water. The amount of saline used was the same as the amount of excess sludge passed through the electrolytic treatment tank. Tables 1 and 2 show the conditions of the diaphragm electrolysis treatment and the properties of the obtained electrolyzed water (alkaline water and acidic oxidized water). In the experiment, wastewater from Food Company A was used as raw water (pH 6.4, BOD 500 mg / liter, COD Mn 240 mg / liter, SS 80 mg / liter), and run conditions of Run 1 and Run 2 were the same except that a solubilization step was provided. .
[0012]
[Table 1]

[Table 2]

[0013]
Table 3 shows the properties of the introduced sludge and the treated sludge.
[Table 3]

[0014]
Table 4 shows the experimental results. Table 4 shows that Run1 incorporating the solubilization step produced significantly less sludge than Run2, and there was almost no difference in treated water quality.
[Table 4]

[0015]
Example 2
2, that is, a processing experiment was conducted by providing an experimental apparatus for performing a solubilization treatment by installing an alkali bath and an oxidation bath in series.
The amount of sludge to be introduced into the solubilization process is three times the amount of excess sludge, two thirds (two times the amount of excess sludge) in the first alkaline tank, and one part in the second alkaline tank. / 3 volume were introduced respectively. Further, as in Example 1, the residence time of each treatment tank was 4 hours, and the salt water used was a salt water having a salt concentration of ２ of seawater, and the treatment was performed in the same manner as in Example 1.
Table 5 shows the properties of the introduced sludge and the treated sludge treated by the in-line method.
[Table 5]

[0016]
Table 6 shows the results of the continuous experiment.
[Table 6]

According to the in-line system, the sludge decomposability is increased by performing the alkali treatment and the oxidation treatment in series, and the pH of the oxidation tank becomes neutral. Further, by adding acidic oxidizing water to the alkali sludge, there is an advantage that the chlorine odor can be eliminated and ancillary facilities for odor control can be reduced.
[0017]
【The invention's effect】
According to the present invention, the treatment using an acidic oxidizing agent and an alkali agent can almost completely decompose excess sludge and hardly generate sludge. By using water or alkaline water, it can be easily obtained at low cost.
[Brief description of the drawings]
FIG. 1 is a flow diagram of a sludge volume reduction process used in the treatment method of the present invention.
FIG. 2 is another partial flow process diagram of the solubilization process.
FIG. 3 is another schematic flow chart of the processing method of the present invention.
FIG. 4 is another schematic flow chart of the processing method of the present invention.
[Explanation of symbols]
1: aerobic biological treatment tank, 2: sedimentation tank, 3: solubilization step, 4: first oxidation tank, 4 ': second oxidation tank, 5: first alkali tank, 5': second alkali tank, 6 : Diaphragm electrolyzer, 7: anode compartment, 8: cathode compartment, 9: anode, 10: cathode, 11: diaphragm, 12: organic wastewater, 13: treated water, 14: return sludge, 15: excess sludge, 16, 17: part of excess sludge, 18: solubilized sludge, 19: salt water, 20: acidic oxidized water, 21: alkaline water, 22: pre-aeration tank, 23: conditioning tank

Claims

After treating the organic sewage with an aerobic biological treatment, a part of the obtained sludge is solubilized and returned to the aerobic biological treatment step, wherein the solubilizing treatment is an acidic oxidizing treatment using an acidic oxidizing agent. A method for treating organic sewage , comprising a step and an alkaline treatment step using an alkaline agent , wherein the acidic oxidant and the alkaline agent are acidic oxidized water and alkaline water obtained by subjecting salt water to diaphragm electrolysis .

The method for treating organic wastewater according to claim 1, wherein the solubilized sludge is subjected to an aeration treatment by providing a pre-aeration step before returning to the aerobic biological treatment step.

The method according to claim 1 or 2 , wherein a part of the solubilized sludge is returned to the step of solubilizing and treated again.

A biological treatment tank for aerobic biological treatment of organic wastewater, a solid-liquid separation device for solid-liquid separation of the biologically treated treatment liquid, and a liquefaction treatment means for solubilizing a part of the solid-liquid separated sludge; in the processing apparatus of the organic wastewater and a flow path for returning the solubilized treated process liquid in the aerobic biological treatment tank, wherein the solubilization treatment means, Rua using acidic oxidation treatment tank and alkaline agent an acidic oxidizing agent and alkali treatment tank, acidic oxidation processing tank, and alkaline treatment tank organic wastewater treatment apparatus for an acidic oxidizing agent and alkali agent and a membrane electrolysis apparatus water is supplied, wherein formed Rukoto to.