JPH05119B2

JPH05119B2 -

Info

Publication number: JPH05119B2
Application number: JP1112087A
Authority: JP
Inventors: Katsuyuki Kataoka
Original assignee: Ebara Research Co Ltd; Ebara Infilco Co Ltd
Current assignee: Ebara Corp; Ebara Research Co Ltd
Priority date: 1989-05-02
Filing date: 1989-05-02
Publication date: 1993-01-05
Also published as: JPH02293095A

Description

[Detailed description of the invention]

〔産業上の利用分野〕本発明は、し尿、下水などの各種有機性汚水の
処理方法に係り、特に、有機性汚水を活性汚泥法
などにより、好気性生物処理を行う際に発生する
余剰汚泥を大幅に減少させ、汚泥処理を合理化す
る新規方法に関する。〔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／KgBDD）程度となることが良く
知られている。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つている。〔発明が解決しようとする課題〕本発明は、上記のような従来技術の問題点を解
決し、余剰汚泥の発生量を著しく減少させること
が可能な新規方法を提供することを目的とする。〔課題を解決するための手段〕上記目的を達成するために、本発明では、有機
性汚水を好気性生物処理したのち、固液分離し、
該分離された汚泥の一部を、前記好気性生物処理
工程にリサイクルする一方、残りの汚泥を２分割
し、片方に酸を添加してPH３以下にし、他方にア
ルカリを添加してPH10以上とし、各々、撹拌滞留
せしめて可溶化したのち、該酸処理汚泥とアルカ
リ処理汚泥とを混合し、混合液を前記好気性生物
処理工程に供給することを特徴とする有機性汚水
の処理方法としたものである。そして、上記の酸およびアルカリによる可溶化
工程は、50℃以上の温度で行うのがよい。次に、本発明の第１図を参照して詳しく説明す
る。以下は、し尿処理を例に挙げて説明している。第１図は、本発明の処理方法を示す工程図であ
る。除渣し尿１は、生物学的硝化脱窒槽２に流入
し、硝化・脱窒素されたのち、流出する活性汚泥
スラリー３が限外ろ過膜（UF）４によつて、完
全にSSが捕捉除去され、清澄な生物処理水５と
UF分離スラリー６となる。なお、固液分離の手
段は、図示例の限外ろ過膜等の膜分離にかえて、
公知の沈降分離、遠心分離等の分離手段でもかま
わない。 UF分離スラリー６の一部７は、硝過脱窒槽２
の活性汚泥濃度を所定濃度に維持するために、返
送される。他部８は、２分割され酸による汚泥の
可溶化槽９およびアルカリによる汚泥の可溶化槽
１０に供給される。９′，１０′は各々鉱酸および
水酸化アルカリである。しかして、酸又はアルカリによる汚泥の可溶化
槽９，１０において汚泥中の有機物の加水分解反
応を進行させる。活性汚泥は炭水化物、たん白
質、脂質から構成されており、活性汚泥細胞の外
層には、菌体外高分子（バイオポリマ）が多量に
存在しているが、強酸性あるいは強アルカリ性の
雰囲気にさらされると、これらの活性汚泥菌体を
構成しているバイオポリマー、炭水化物、蛋白質
などが加水分解を受け、低分子化されて分子コロ
イド状になり、可溶化される。低分子化された可溶化有機コロイドは、微生物
による資化性が顕著に向上するのでこれらを、再
び活性汚泥が存在する硝化脱窒槽２に返送供給す
ると、可溶化された有機物は活性汚泥（主に脱窒
素菌）によつて資化されて、最終的にCO₂とH₂O
に分解される。この結果、余剰活性汚泥の発生量
が減少する。本発明においては、化溶化対象汚泥を２分割
し、各々について酸あるいはアルカリによる加水
分解を行つたのち、これらを合流混合させてから
硝化脱窒槽２に供給することが重要である。もしも、酸処理のみ、あるいはアルカリによる
可溶化処理のみを行つてから、可溶化汚泥を硝化
脱窒槽２に流入させると、硝化脱窒槽２のPHが酸
性あるいはアルカリ性にかたよつてしまい、硝化
脱窒菌にとつて好適なPH条件（中性）から偏寄し
てしまい、硝化脱窒反応が著しく悪化する。しかるに、本発明では、酸可溶化汚泥とアルカ
リ可溶化汚泥とを合流し、撹拌槽１１で混合中和
してから、生物処理槽２に返送するので、このよ
うなトラブルを招かない。しかも、酸による化溶化法単独あるいはアルカ
リによる可溶化法単独では、それぞれ、可溶化処
理のあとで、アルカリ剤又は酸による中和を行う
必要があり、このアルカリまたは、酸は単に中和
剤として使われるだけで、汚泥の可溶化に寄与し
ないため、いたずらに薬品コストが増加するとい
う欠点がある。これに対し、本発明では、こうし
た欠点がない。しかして、本発明による方法を採用すると、従
来プロセスに比較して、余剰汚泥の発生量が減少
するが、酸又はアルカリによつても可溶化しない
汚泥は、不可避的に余剰汚泥となるので、管路１
２あるいは１２′より、余剰汚泥を抜き出し、汚
泥脱水工程１３に供給し、脱水汚泥１４と脱水分
離液１５に分離する。脱水分離液１５は生物処理
槽２に供給されて処理される。なお、酸またはアルカリによる可溶化のPHの最
適条件は、実験の結果から、酸の場合はPH３以
下、アルカリ可溶化法の場合はPH以上であり、さ
らに温度条件としては、50℃以上、混和時間は３
〜48hr（汚泥性状によつて異なる）が好適である
ことが認められた。温度と滞留時間の適正値は、汚泥の性状によつ
て、大きく変化するので一概には決定できない
が、汚泥の可溶化率50％以上を得るためには、PH
３以下又はPH10以上の条件が不可欠であることが
また温度は50℃以上が好ましいことが認められ
た。また、可溶化処理と同時に、もしくは先立つ
て、超音波処理を行うと可溶化効果がやや向上す
ることも認められた。〔実施例〕以下、実施例により、本発明を詳述するが、本
発明はこれらの実施例に限定されない。実施例１表１に示す水質の除渣し尿を表２に示す処理条
件で無希釈で生物学的硝化脱窒処理を行つた。 [Industrial Application Field] The present invention relates to a method for treating various organic sewage such as human waste and sewage, and in particular, the present invention relates to a method for treating various organic sewage such as human waste and sewage. Concerning a new method for significantly reducing sludge treatment and streamlining sludge treatment. [Conventional technology] Conventionally, the biggest problem with aerobic biological treatment of organic wastewater (activated sludge method, biological nitrification and denitrification method, etc.) was not in the water purification process, but rather in the sludge treatment. It's in the process. That is, the biggest problem with the aerobic biological treatment method is that it generates a very large amount of surplus activated sludge. Currently, surplus activated sludge is dehydrated and then landfilled or incinerated, but this requires a great deal of expense and equipment. Based on numerous experiments and results, the amount of surplus sludge generated by the conventional activated sludge method is estimated to be
It is well known that it is approximately 0.6 to 0.8 (KgSS/KgBDD). Furthermore, surplus sludge is qualitatively difficult to dewater, making sludge treatment increasingly difficult. [Problems to be Solved by the Invention] An object of the present invention is to provide a new method that can solve the problems of the prior art as described above and significantly reduce the amount of surplus sludge generated. [Means for Solving the Problems] In order to achieve the above object, the present invention subjects organic wastewater to aerobic biological treatment, and then performs solid-liquid separation,
A part of the separated sludge is recycled to the aerobic biological treatment process, while the remaining sludge is divided into two, acid is added to one side to make it PH3 or less, and alkali is added to the other side to make it PH10 or more. A method for treating organic sewage is characterized in that the acid-treated sludge and the alkali-treated sludge are mixed after being stirred and retained for solubilization, and the mixed liquid is supplied to the aerobic biological treatment step. It is something. The acid and alkali solubilization step described above is preferably performed at a temperature of 50°C or higher. Next, the present invention will be explained in detail with reference to FIG. The following is an explanation using human waste treatment as an example. FIG. 1 is a process diagram showing the treatment method of the present invention. The filtered human waste 1 flows into the biological nitrification and denitrification tank 2 where it is nitrified and denitrified, and then the activated sludge slurry 3 that flows out is completely captured and removed by an ultrafiltration membrane (UF) 4. and clear biologically treated water5
This becomes UF separation slurry 6. Note that the means of solid-liquid separation may be replaced by membrane separation such as an ultrafiltration membrane in the illustrated example.
Any known separation means such as sedimentation or centrifugation may be used. A portion 7 of the UF separation slurry 6 is transferred to the nitrification and denitrification tank 2
The activated sludge is sent back to maintain the activated sludge concentration at a predetermined concentration. The other portion 8 is divided into two parts and supplied to an acid sludge solubilization tank 9 and an alkali sludge solubilization tank 10. 9' and 10' are a mineral acid and an alkali hydroxide, respectively. Thus, the hydrolysis reaction of organic matter in the sludge proceeds in the sludge solubilization tanks 9 and 10 using acid or alkali. Activated sludge is composed of carbohydrates, proteins, and lipids, and the outer layer of activated sludge cells contains a large amount of extracellular polymers (biopolymers), but they cannot be exposed to strongly acidic or alkaline atmospheres. When the biopolymers, carbohydrates, proteins, etc. that make up these activated sludge cells are hydrolyzed, they are reduced to a molecular colloid and solubilized. The ability of solubilized organic colloids reduced to low molecular weight to be assimilated by microorganisms is significantly improved, so when these are returned to the nitrification-denitrification tank 2 where activated sludge is present, the solubilized organic matter is converted into activated sludge (mainly activated sludge). denitrifying bacteria), and finally CO ₂ and H ₂ O
It is decomposed into As a result, the amount of surplus activated sludge generated is reduced. In the present invention, it is important to divide the sludge to be solubilized into two parts, hydrolyze each part with acid or alkali, and then mix them together before supplying them to the nitrification-denitrification tank 2. If the solubilized sludge is allowed to flow into the nitrification-denitrification tank 2 after performing only acid treatment or only solubilization treatment with alkali, the pH of the nitrification-denitrification tank 2 will become acidic or alkaline, and the nitrification-denitrification bacteria will The PH conditions (neutral) that are suitable for the nitrification and denitrification reaction will be significantly deteriorated. However, in the present invention, the acid-solubilized sludge and the alkali-solubilized sludge are combined, mixed and neutralized in the stirring tank 11, and then returned to the biological treatment tank 2, so such troubles are not caused. Moreover, in the solubilization method using acid alone or the solubilization method using alkali alone, it is necessary to perform neutralization with an alkali agent or acid after the solubilization treatment, and this alkali or acid is used only as a neutralizing agent. Since it does not contribute to the solubilization of sludge even if it is used, it has the disadvantage of unnecessarily increasing chemical costs. In contrast, the present invention does not have these drawbacks. Therefore, when the method according to the present invention is adopted, the amount of surplus sludge generated is reduced compared to the conventional process, but since sludge that cannot be solubilized even by acid or alkali inevitably becomes surplus sludge, Conduit 1
Excess sludge is extracted from 2 or 12' and supplied to a sludge dewatering step 13, where it is separated into dehydrated sludge 14 and dehydrated separated liquid 15. The dehydrated separated liquid 15 is supplied to the biological treatment tank 2 and treated. The optimum pH conditions for acid or alkali solubilization are 3 or less for acid and PH or more for alkali solubilization, as well as temperature conditions of 50°C or higher and miscibility. time is 3
~48 hours (depending on sludge properties) was found to be suitable. Appropriate values for temperature and residence time cannot be determined unconditionally because they vary greatly depending on the properties of the sludge, but in order to obtain a sludge solubilization rate of 50% or more, the PH
It was recognized that conditions of pH 3 or lower or pH 10 or higher are essential, and that a temperature of 50°C or higher is preferable. It was also observed that the solubilization effect was slightly improved when ultrasonication was performed simultaneously with or prior to the solubilization treatment. [Examples] Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 A biological nitrification and denitrification treatment was performed on the filtered human waste having the water quality shown in Table 1 under the treatment conditions shown in Table 2 without dilution.

【表】【table】

【表】その後、活性汚泥スラリーをUF膜（限外ろ過
膜）で固液分離し、汚泥固形物濃度2.0〜2.2％の
UF分離汚泥を得た。このうちの50％の生物学的硝化脱窒槽に返送す
る一方、残りの50％のUF分離汚泥を２等分し、
片方にHClを添加し、PH2.0とした。他方の汚泥
にNaOHを添加し、PH11とし、酸又はアルカリ
添加汚泥を70℃に加温しつつ24hr混和滞留させ
て、汚泥を可溶化した。次の式で定義される汚泥
可溶化率は、HCl処理の場合55％、アルカリ処理
の場合78％となつた。汚泥可溶化率＝１−（可溶化後の固形物濃度／UF分離
汚泥固形物濃度）しかるのち、両汚泥を混合し、中和せしめた結
果、中和汚泥のPHは5.2〜5.8となつた。この中和
汚泥を前記の生物学的硝化脱窒処理槽に供給し
て、６ケ月間のロングランテストを行つた。この結果、生物学的硝化脱窒工程のMLSS濃度
を設定値に維持するのに必要な余剰汚泥引抜き量
は、し尿１m³あたり、2.5〜3.1（Kgd.sol：ds／m³）
であつた。また、UF膜透過水の水質は表−３の左欄とな
つた。比較例１実施例１における、酸可溶化およびアルカリ可
溶化処理工程を省略した以外は、全く同一の条件
で実施例１の実験とパラレルに実験し、これを対
照実験とした。この結果６ケ月の余剰汚泥の発生量は4.9〜6.6
Kg・ds／m³となり、本発明に比較し、約２倍の余
剰汚泥発生量となつた。またUF膜透過水の水質は、表−３の左欄とな
つた。[Table] After that, the activated sludge slurry is separated into solid and liquid using a UF membrane (ultrafiltration membrane), and the sludge solids concentration is 2.0 to 2.2%.
UF separated sludge was obtained. Of this, 50% is returned to the biological nitrification-denitrification tank, while the remaining 50% of the UF separated sludge is divided into two equal parts.
HCl was added to one side to adjust the pH to 2.0. NaOH was added to the other sludge to adjust the pH to 11, and the acid- or alkali-added sludge was mixed and retained for 24 hours while being heated to 70°C to solubilize the sludge. The sludge solubilization rate defined by the following formula was 55% for HCl treatment and 78% for alkaline treatment. Sludge solubilization rate = 1 - (solid concentration after solubilization/UF separated sludge solid concentration) After that, both sludges were mixed and neutralized, and as a result, the pH of the neutralized sludge was 5.2 to 5.8. . This neutralized sludge was supplied to the biological nitrification and denitrification treatment tank, and a long run test for 6 months was conducted. As a result, the amount of excess sludge extracted to maintain the MLSS concentration in the biological nitrification and denitrification process at the set value is 2.5 to 3.1 (Kgd.sol: ds/m ³ ) per 1 m ³ of human waste.
It was hot. In addition, the water quality of the UF membrane permeate water is shown in the left column of Table 3. Comparative Example 1 An experiment was carried out in parallel to the experiment of Example 1 under exactly the same conditions except that the acid solubilization and alkali solubilization treatment steps in Example 1 were omitted, and this was used as a control experiment. As a result, the amount of surplus sludge generated in 6 months is 4.9 to 6.6
Kg・ds/m ³ , and the amount of surplus sludge generated was approximately twice that of the present invention. The quality of the water permeated through the UF membrane was as shown in the left column of Table 3.

〔Effect of the invention〕

本発明によれば、次のような効果を奏する。余剰活性汚泥の発生量が減少し、汚泥処理工
程が運転費、設備費ともに合理化される。汚泥の可溶化のあとの中和用の薬品を必要と
しないので、運転経費が節減される。 According to the present invention, the following effects are achieved. The amount of surplus activated sludge generated is reduced, and the sludge treatment process is streamlined in terms of operating costs and equipment costs. Operating costs are reduced as no neutralizing chemicals are required after sludge solubilization.

[Brief explanation of the drawing]

第１図は本発明の処理方法を示す工程図であ
る。１……有機性汚水（除渣し尿）、２……好気性
生物処理槽（生物学的硝化脱窒槽）、３……活性
汚泥スラリー、４……固液分離工程（限外ろ過
槽）、５……清澄な処理水、６……分離汚泥、７
……返送汚泥、９……酸可溶化槽、１０……アル
カリ可溶化槽、１１……撹拌混合槽、１３……汚
泥脱水工程、１４……脱水汚泥。 FIG. 1 is a process diagram showing the treatment method of the present invention. 1...Organic sewage (removed human waste), 2...Aerobic biological treatment tank (biological nitrification and denitrification tank), 3...Activated sludge slurry, 4...Solid-liquid separation process (ultrafiltration tank), 5... Clear treated water, 6... Separated sludge, 7
... Return sludge, 9 ... Acid solubilization tank, 10 ... Alkali solubilization tank, 11 ... Stirring mixing tank, 13 ... Sludge dewatering process, 14 ... Dewatered sludge.

Claims

[Scope of Claims] 1 After subjecting organic sewage to aerobic biological treatment, solid-liquid separation is performed, and a portion of the separated sludge is recycled to the aerobic biological treatment process, while the remaining sludge is divided into two. Then, add acid to one side to make it below PH3,
The sludge is characterized by adding an alkali to the other to make it PH10 or higher, stirring and retaining each to solubilize, and then mixing the acid-treated sludge and the alkali-treated sludge, and supplying the mixed liquid to the aerobic biological treatment step. How to treat organic wastewater. 2 The solubilization step with acid and alkali,
Claim 1 characterized in that the process is carried out at a temperature of 50°C or higher.
The method for treating organic sewage described.