JP3825021B2 - Organic wastewater treatment apparatus and organic wastewater treatment method - Google Patents

Organic wastewater treatment apparatus and organic wastewater treatment method Download PDF

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JP3825021B2
JP3825021B2 JP2003296315A JP2003296315A JP3825021B2 JP 3825021 B2 JP3825021 B2 JP 3825021B2 JP 2003296315 A JP2003296315 A JP 2003296315A JP 2003296315 A JP2003296315 A JP 2003296315A JP 3825021 B2 JP3825021 B2 JP 3825021B2
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恒美 大岩
秀樹 西濱
直人 安田
直樹 原村
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日立マクセル株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

本発明は、有機性汚水の微生物処理により生じる余剰汚泥を削減するシステムに関するものであり、さらに詳しくは、これまで廃棄していた余剰汚泥を酸性領域で、塩化物添加の雰囲気で電解(「電気分解」を簡略化して「電解」で表す)により微生物を死滅させた後、再び曝気槽に返送し、これらの処理により、廃棄する余剰汚泥を効率よく削減できるようにするシステムに関するものである。   The present invention relates to a system for reducing surplus sludge generated by microbial treatment of organic wastewater. More specifically, surplus sludge that has been disposed so far is electrolyzed in an acidic region in an atmosphere containing chloride (“electricity” The present invention relates to a system in which microorganisms are killed by simplifying “decomposition” (represented by “electrolysis”), then returned to the aeration tank again, and excess sludge to be discarded can be efficiently reduced by these treatments.
有機性汚水の微生物処理では、汚水中に存在する可溶性有機物を微生物が消化処理する一方で微生物の増殖を引き起こす。この増殖した微生物を含む汚泥はいわゆる余剰汚泥として排出する必要がある。この余剰汚泥は脱水処理した後にそのまま埋立処分されるか、または焼却処分されているが、余剰汚泥は難脱水性であるため、脱水処理した後でも70〜80質量%の水分を有するのが通常である。従って、これをそのまま埋立処分するにしても固形分20〜30質量%程度のものを運搬し埋め立てることになり、その質量および体積の大半が大部分を占める水分の搬送費および埋立費として費やされているのが現状である。また、焼却処分するにしても同様で余剰汚泥中に多量に存在する水分のためにその乾燥および蒸発潜熱にエネルギーの大半が費やされているのが現状であって、その費用は高額なものとなっている。   In microbial treatment of organic sewage, the microorganisms digest the soluble organic matter present in the sewage while causing microbial growth. The sludge containing the grown microorganisms needs to be discharged as so-called surplus sludge. This surplus sludge is either landfilled or decommissioned after being dehydrated, but the surplus sludge is hardly dehydrated and therefore usually has a water content of 70 to 80% by mass even after dehydration. It is. Therefore, even if this is landfilled as it is, it will be transported and landfilled with a solid content of about 20 to 30% by mass, and the mass and volume of the majority will be spent as moisture transportation and landfill costs. This is the current situation. In addition, even if it is incinerated, most of the energy is spent on drying and latent heat of evaporation due to the large amount of moisture in the excess sludge, and the cost is high. It has become.
これら余剰汚泥の量は年々増加の一途をたどっており、前記埋立処分するにしても焼却処分にしてもいずれも処理費用の占める割合が高く、また埋立場所の確保や焼却残さの処理など、経済面および環境面の両面において問題が顕在化している。   The amount of excess sludge has been increasing year by year, and the disposal cost is high for both landfill disposal and incineration. The problem has become obvious in both environmental and environmental aspects.
こうした背景の下で、この余剰汚泥の処理に微生物処理を有効に活用することが検討されている。余剰汚泥はその中に含まれている微生物を一旦死滅させれば有機物の消化処理同様に活性汚泥により消化処理されることはよく知られている。可溶性有機物の消化処理により増殖した余剰汚泥を死滅させた後、曝気槽(活性汚泥槽)に返送することで微生物が消化処理を行い、余剰汚泥を減量化(または減容化)する。すなわち、余剰汚泥を微生物に消化処理させることで、死滅した余剰汚泥はCOとHOとに分解され減量化される。 Under such a background, effective utilization of microbial treatment for the treatment of surplus sludge has been studied. It is well known that surplus sludge is digested with activated sludge in the same manner as organic matter digestion once the microorganisms contained therein are killed. After the surplus sludge grown by the digestion process of the soluble organic matter is killed, the microorganism is digested by returning it to the aeration tank (activated sludge tank), and the surplus sludge is reduced (or reduced in volume). That is, the surplus sludge that has been killed is decomposed into CO 2 and H 2 O and reduced in quantity by digesting the surplus sludge with microorganisms.
余剰汚泥を減量化させる手段としては、種々の方法が提案されており、オゾン酸化法、過酸化水素酸化法、次亜塩素酸酸化法、酸・アルカリ処理法、熱処理法などが提案されている。   Various methods have been proposed for reducing excess sludge, such as ozone oxidation, hydrogen peroxide oxidation, hypochlorous acid oxidation, acid / alkali treatment, and heat treatment. .
しかしながら、上記の処理方法は、いずれも薬品やエネルギーを大量に使用したり、装置が大掛かりになったりするため、必ずしも満足のいく方法とはいえなかった。   However, none of the above-mentioned treatment methods are always satisfactory because they use a large amount of chemicals and energy or require a large apparatus.
上記の方法の中でも、電解により次亜塩素酸イオンや次亜塩素酸を生成させて余剰汚泥を減量化させる方法が比較的ランニングコストが安いといわれている(例えば、特許文献1、2参照)。   Among the above methods, it is said that a method of reducing excess sludge by generating hypochlorite ions or hypochlorous acid by electrolysis is relatively low in running cost (see, for example, Patent Documents 1 and 2). .
しかしながら、これらの方法では、アルカリを使用して余剰汚泥の減量化を図っており、特に特許文献2では電極間に隔壁を設けて、次亜塩素酸とアルカリとを生成させ、それらの次亜塩素酸とアルカリとを用いて余剰汚泥の減量化を図っているため、減量化という点では効果があるものの、微生物を死滅させる効果(殺菌効果)は充分とは言えなかった。   However, in these methods, the amount of excess sludge is reduced by using an alkali. In particular, in Patent Document 2, a partition wall is provided between the electrodes to generate hypochlorous acid and an alkali, and the hypochlorite thereof. Since the amount of excess sludge is reduced using chloric acid and alkali, it is effective in terms of weight reduction, but the effect of killing microorganisms (bactericidal effect) is not sufficient.
すなわち、アルカリを使用すると、減量化に適しているものの、微生物の死滅効果は、酸性側で処理する場合より低くなり、そのため、アルカリで処理した余剰汚泥を再び曝気槽に返送して消化処理させると、消化効率が悪くなって、曝気槽での負荷を高め、曝気槽を大きくしなければならないという問題があった。   That is, when alkali is used, it is suitable for weight reduction, but the effect of killing microorganisms is lower than when it is treated on the acidic side. Therefore, surplus sludge treated with alkali is returned to the aeration tank and digested. As a result, the digestion efficiency deteriorates, and there is a problem that the load on the aeration tank must be increased and the aeration tank must be enlarged.
そこで、微生物を死滅させるために強酸性にすると、その微生物の死滅処理後の汚泥を曝気槽に返送する際に再度アルカリ性の薬品を添加して中性に戻す必要がある。これは返送した汚泥により曝気槽の条件が消化処理に適さない条件に変化するためであって、熱処理やオゾン酸化処理などもこれと同様の問題があり、曝気槽に殺菌後そのまま返送できることがランニングコストを抑える決めてとなる。   Therefore, if a strong acid is used to kill the microorganism, it is necessary to add an alkaline chemical again to return the sludge after the killing treatment of the microorganism to the aeration tank. This is because the conditions of the aeration tank change to conditions that are not suitable for digestion due to the returned sludge, and there are similar problems with heat treatment and ozone oxidation treatment, and it is possible to return to the aeration tank as it is after sterilization. Decide to keep costs down.
特開2002−126782号公報JP 2002-126782 A 特開平10−76299号公報JP-A-10-76299
本発明は、上記のような従来の有機性汚水の処理時における問題点を解決し、余剰汚泥中の微生物を効率的に死滅化させ、かつ、ランニングコストが低く、有機性汚水の微生物処理により生じる余剰汚泥を効率よく削減できる有機性汚水の処理装置および処理方法を提供することを目的とする。   The present invention solves the problems in the conventional treatment of organic sewage as described above, efficiently kills microorganisms in excess sludge, and has a low running cost, by microbial treatment of organic sewage. An object of the present invention is to provide an organic sewage treatment apparatus and a treatment method capable of efficiently reducing excess sludge generated.
本発明の有機性汚水の処理装置は、有機性汚水を微生物処理して活性汚泥含有水を得るための曝気槽と、上記曝気槽で得られた活性汚泥含有水を、重力沈降法によって固形分濃度が0.3〜2質量%になるように濃縮して、濃縮汚泥と上澄液とに分離するための沈殿槽と、濃縮汚泥の一部を曝気槽に返送する機構と、残りの濃縮汚泥を余剰汚泥とし、その余剰汚泥に塩化物を0.1〜3質量%添加するとともに、酸を添加してpHを2〜6に調整する機構と、電極を備えており、上記余剰汚泥に1〜40mA/cm2の電流密度で電解処理を施して、余剰汚泥中の微生物を殺菌するための電解槽と、上記電解処理した余剰汚泥を再び曝気槽に返送する機構とを有することを特徴とするものである。   The organic sewage treatment apparatus of the present invention comprises an aeration tank for microbial treatment of organic sewage to obtain activated sludge-containing water, and activated sludge-containing water obtained in the above-mentioned aeration tank with a solid content by gravity sedimentation. Concentrating to a concentration of 0.3-2% by mass and separating it into concentrated sludge and supernatant, a mechanism for returning a part of the concentrated sludge to the aeration tank, and the remaining concentration Sludge is used as surplus sludge, and 0.1 to 3% by mass of chloride is added to the surplus sludge, and a mechanism for adjusting the pH to 2 to 6 by adding acid and an electrode are provided. Electrolytic treatment is performed at a current density of 1 to 40 mA / cm2 to sterilize microorganisms in the excess sludge, and a mechanism for returning the electrolytically treated excess sludge to the aeration tank again is provided. To do.
また、本発明の有機性汚水の処理方法は、有機性汚水の微生物処理により生じる余剰汚泥を削減するための処理方法であって、曝気槽で微生物処理された活性汚泥含有水を沈殿槽で重力沈降法によって活性汚泥中の固形分濃度が0.3〜2質量%になるように濃縮して濃縮汚泥と上澄液とに分離し、濃縮汚泥の一部を曝気槽に返送する第一工程、残りの濃縮汚泥を余剰汚泥とし、その余剰汚泥に塩化物を0.1〜3質量%添加するとともに、酸を添加してpH2〜6に調整する第二工程、電解槽中で電極を用いて上記余剰汚泥に1〜40mA/cmの電流密度で電解処理を施し、余剰汚泥中の微生物を殺菌する第三工程、上記電解処理した余剰汚泥を再びオキシデーション・リッチ槽などの曝気槽に返送する第四工程を繰り返すことによって、有機性汚水の微生物処理により生じる余剰汚泥を削減ことのできる処理方法である。 Further, the organic sewage treatment method of the present invention is a treatment method for reducing excess sludge generated by microbial treatment of organic sewage, and the activated sludge-containing water that has been microbially treated in the aeration tank is gravity-treated in the precipitation tank. The first step of concentrating the activated sludge so that the solid content concentration in the activated sludge is 0.3-2% by mass, separating it into concentrated sludge and supernatant, and returning a part of the concentrated sludge to the aeration tank. The remaining concentrated sludge is used as surplus sludge, and 0.1 to 3% by mass of chloride is added to the surplus sludge and the acid is added to adjust the pH to 2 to 6, using the electrode in the electrolytic cell. The surplus sludge is subjected to electrolytic treatment at a current density of 1 to 40 mA / cm 2 to sterilize microorganisms in the surplus sludge, and the surplus sludge subjected to the electrolytic treatment is again put into an aeration tank such as an oxidation rich tank. By repeating the fourth step to return Thus, it is a treatment method capable of reducing excess sludge generated by microbial treatment of organic wastewater.
本発明においては、前記余剰汚泥に添加する塩化物は塩化ナトリウム、塩化カリウム、塩化マグネシウム、塩化カルシウムから選ばれることが好ましく、酸は硫酸、塩酸から選ばれることが好ましく、前記電解処理に用いる電極はアモルファスカーボン、グラファイトなどの炭素系材料からなるか、またはチタン板、ステンレス鋼板などの金属板上に上記炭素系材料をコーティングしたものからなるか、または上記金属板に直接もしくは上記金属板にコーティングした上記炭素系材料上にさらにダイヤモンドもしくはダイヤモンドライクカーボンをコーティングしたものからなることが好ましい。また、電解処理する余剰汚泥は10〜40℃の範囲に保持することが好ましい。   In the present invention, the chloride added to the excess sludge is preferably selected from sodium chloride, potassium chloride, magnesium chloride, and calcium chloride, and the acid is preferably selected from sulfuric acid and hydrochloric acid. The electrode used for the electrolytic treatment Is made of a carbon-based material such as amorphous carbon or graphite, or a metal plate such as a titanium plate or stainless steel plate coated with the carbon-based material, or directly or coated on the metal plate. The carbon-based material is preferably further coated with diamond or diamond-like carbon. Moreover, it is preferable to hold | maintain the excess sludge which carries out an electrolytic treatment in the range of 10-40 degreeC.
また、本発明においては、前記電解処理に用いる電源が直流電源であって、その直流をそのまま用いるか、またはその直流に一定時間毎に逆電圧を印加して用いることが好ましく、また、電解処理の前後で、余剰汚泥中に占める不溶解性有機物の含有量の減少率が25質量%以下であることが好ましい。更に、前記曝気槽としては、オキシデーション・ディッチが好ましい。加えて、前記電解処理を行うための電解槽内の電極間には、隔膜を設けないことが好ましい。   In the present invention, the power source used for the electrolytic treatment is a direct current power source, and it is preferable to use the direct current as it is or to apply a reverse voltage to the direct current at regular intervals. Before and after, it is preferable that the decreasing rate of the content of the insoluble organic matter in the excess sludge is 25% by mass or less. Further, as the aeration tank, an oxidation ditch is preferable. In addition, it is preferable not to provide a diaphragm between the electrodes in the electrolytic cell for performing the electrolytic treatment.
前記電解処理の前後で、余剰汚泥中に占める不溶解性有機物の含有量の減少率が25質量%以下であることが好ましいとしているのは、本発明者らが見出したものであって、次の理由によるものである。すなわち、曝気槽での消化処理をスムーズに行わせるためには、活性汚泥中の有機物は溶解性の有機物であることが必要である。そのため、活性汚泥中の微生物を死滅させて不溶解性の有機物をできるだけ溶解性の有機物に変えておく必要があるが、その際に、本発明者らは、微生物の細胞膜ないしは細胞壁に傷をつけた状態で微生物を死滅させると、消化できない不溶解性の細胞壁などの有機物が曝気槽でいつまでも消化処理されずに残存し、曝気槽での負荷を増加させることを見出した。従って、微生物の細胞壁を部分的に破壊して微生物を死滅させるのではなく、細胞壁を傷つけずにプロテアーゼにより内部から細胞壁を溶解させることが好ましく、それが不溶解性の有機物を溶解性の有機物に効率よく変える有効な手段であることを見出したのである。そして、その際の判断基準として、不溶解性有機物の電解処理での減少が25質量%以下にすることが好ましく、20質量%以下にすることがより好ましい。本発明は、上記のように活性汚泥の処理技術を改良することにより、有機性汚水の微生物処理により生じる余剰汚泥を従来より効率よく削減できるようにしているのである。   The inventors have found that the rate of decrease in the content of insoluble organic matter in the excess sludge before and after the electrolytic treatment is preferably 25% by mass or less. This is because of the reason. That is, in order to smoothly perform the digestion process in the aeration tank, the organic matter in the activated sludge needs to be a soluble organic matter. For this reason, it is necessary to kill microorganisms in activated sludge and change insoluble organic substances to soluble organic substances as much as possible. At this time, the present inventors have damaged the cell membrane or cell wall of microorganisms. It has been found that when microorganisms are killed in a state where they are dead, organic substances such as insoluble cell walls that cannot be digested remain in the aeration tank indefinitely, increasing the load in the aeration tank. Therefore, it is preferable to dissolve the cell wall from the inside by protease without damaging the cell wall by partially destroying the cell wall of the microorganism, without damaging the cell wall, which makes insoluble organic matter into soluble organic matter. They found it to be an effective means of changing efficiently. And as a judgment standard in that case, it is preferable to make the reduction | decrease in electrolytic treatment of an insoluble organic substance into 25 mass% or less, and it is more preferable to set it as 20 mass% or less. The present invention improves the activated sludge treatment technology as described above, thereby making it possible to more efficiently reduce the excess sludge produced by the microbial treatment of organic wastewater than before.
本発明によれば、有機性汚水の微生物処理により生じる余剰汚泥を効率よく削減することができる。   According to the present invention, it is possible to efficiently reduce excess sludge generated by microbial treatment of organic wastewater.
すなわち、曝気槽で得られた活性汚泥含有液を濃縮することにより、余剰汚泥の処理効率を高めることができ、余剰汚泥のpHを2〜6と酸性にすることにより余剰汚泥の粘性を低下させ、かつ塩化物の添加により殺菌作用の高い次亜塩素酸を効率的に発生させて、電解処理効率を向上させ、余剰汚泥を効率よく溶解性の有機物に変化させ、曝気槽での分解をしやすくして、有機性汚水の微生物処理により発生する余剰汚泥を効率よく削減することができる。   That is, by concentrating the activated sludge-containing liquid obtained in the aeration tank, it is possible to increase the treatment efficiency of the excess sludge, and by reducing the viscosity of the excess sludge by making the pH of the excess sludge 2-6. In addition, the addition of chloride efficiently generates hypochlorous acid with high bactericidal action, improves the electrolytic treatment efficiency, efficiently converts excess sludge into soluble organic matter, and decomposes it in the aeration tank. This makes it possible to efficiently reduce excess sludge generated by microbial treatment of organic wastewater.
以下、本発明の好適な実施形態を、図1を用いて説明する。   Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG.
図1は、本発明の装置および方法の処理プロセスの概要を示す図である。   FIG. 1 is a diagram showing an outline of a processing process of the apparatus and method of the present invention.
上記処理プロセスにおいて、まず、有機性汚水1は曝気槽2に導入され、その曝気槽2中で微生物によって消化処理される。そして、その曝気槽2から排出された活性汚泥含有液3は沈殿槽4に導入され、その沈殿槽4中で重力沈降法により活性汚泥が沈殿し、濃縮汚泥と上澄液とに分離される。沈殿槽4中の上澄液は処理済水5として沈殿槽4から排出され、この処理済水5は殺菌して系外に放出される。   In the treatment process, first, the organic sewage 1 is introduced into the aeration tank 2 and digested by microorganisms in the aeration tank 2. And the activated sludge containing liquid 3 discharged | emitted from the aeration tank 2 is introduce | transduced into the settling tank 4, and activated sludge precipitates by the gravity sedimentation method in the settling tank 4, and is isolate | separated into a concentrated sludge and a supernatant liquid. . The supernatant liquid in the settling tank 4 is discharged from the settling tank 4 as treated water 5, and the treated water 5 is sterilized and discharged out of the system.
そして、沈殿槽4の底部に沈殿して濃度が高くなった活性汚泥は濃縮汚泥6として沈殿槽4から取り出され、そのうちの一部が返送汚泥7として前記曝気槽2に戻される。ここまでのプロセスは従来の有機性汚水の微生物処理の場合と同様であるが、本発明では、この従来プロセスにおける濃縮汚泥の一部を余剰汚泥として引き抜き、その余剰汚泥に特定の態様で電解を施し、余剰汚泥中の微生物を死滅させて、溶解性有機物に変え、そのように処理した余剰汚泥を再び曝気槽に返送し、微生物により消化処理させ、このプロセスを繰り返し行うことにより、余剰汚泥を効率よく削減もしくはほとんどゼロとすることを特徴としている。   Then, the activated sludge that has settled at the bottom of the sedimentation tank 4 and has a high concentration is taken out from the sedimentation tank 4 as concentrated sludge 6, and a part of the sludge is returned to the aeration tank 2 as return sludge 7. The process so far is the same as in the case of the conventional microbial treatment of organic wastewater, but in the present invention, a part of the concentrated sludge in this conventional process is extracted as surplus sludge, and the surplus sludge is electrolyzed in a specific manner. The microorganisms in the excess sludge are killed, converted into soluble organic matter, the surplus sludge so treated is returned to the aeration tank again, digested with microorganisms, and this process is repeated to remove excess sludge. It is characterized by efficient reduction or almost zero.
以下、本発明において要部となる残りのプロセスを順次説明すると、前記残りの濃縮汚泥6は余剰汚泥8として薬剤混合槽9に送られ、その薬剤混合槽9中で上記余剰汚泥8に塩化物が0.1〜3質量%添加され、かつ酸が添加されてpHが2〜6に調整される。   Hereinafter, the remaining processes which are the main part in the present invention will be described in sequence. The remaining concentrated sludge 6 is sent to the chemical mixing tank 9 as surplus sludge 8, and chloride is added to the surplus sludge 8 in the chemical mixing tank 9. Is added in an amount of 0.1 to 3% by mass, and an acid is added to adjust the pH to 2 to 6.
上記のように、沈殿により生じた濃縮汚泥6を余剰汚泥8として薬剤混合槽9に導入する際、その余剰汚泥8の固形分濃度は沈殿槽4の沈殿汚泥の固形分濃度(つまり、濃縮汚泥の固形分濃度)と同様に0.3〜2質量%であることが好ましく、特に0.8〜1.5質量%であることが好ましい。余剰汚泥8の固形分濃度が0.3質量%より低い場合は、電解槽で殺菌(微生物の死滅)処理を行う時に電極の周りの汚泥量が少なくなって殺菌効率が悪くなるおそれがあり、一方、余剰汚泥8の固形分濃度が2質量%より高い場合は、粘度が高くなって攪拌がしにくいため、電解が充分に進行せず、また、電極の周囲に死滅した汚泥が留まり生きた汚泥が電極の周りに集まりにくくなって、殺菌効率が低下する。また、死滅した汚泥が電極の周りに長時間滞在すると、微生物の細胞壁が傷付けられ、プロテアーゼにより内部から細胞壁を溶解させることができなくなって、溶解性有機物に効率よく変えることができなくなるおそれがある。   As described above, when the concentrated sludge 6 generated by precipitation is introduced into the chemical mixing tank 9 as excess sludge 8, the solid content concentration of the excess sludge 8 is the solid content concentration of the precipitated sludge in the precipitation tank 4 (that is, concentrated sludge). The solid content concentration is preferably 0.3 to 2% by mass, and particularly preferably 0.8 to 1.5% by mass. If the solid content concentration of the excess sludge 8 is lower than 0.3% by mass, the amount of sludge around the electrode may be reduced when the sterilization (microbe killing) process is performed in the electrolytic cell, and the sterilization efficiency may deteriorate. On the other hand, when the solid content concentration of the excess sludge 8 is higher than 2% by mass, the viscosity is so high that it is difficult to stir, so that the electrolysis does not proceed sufficiently, and the dead sludge remains around the electrode and remains alive. The sludge becomes difficult to collect around the electrode, and the sterilization efficiency is lowered. In addition, if dead sludge stays around the electrode for a long time, the cell walls of microorganisms are damaged, and the cell walls cannot be dissolved from the inside by proteases, and may not be efficiently converted into soluble organic matter. .
そして、薬剤混合槽9においては、余剰汚泥8に塩として塩化物を添加し、また、酸を添加してpH2〜6に調整する。   And in the chemical | medical agent mixing tank 9, a chloride is added to the excess sludge 8 as a salt, and an acid is added and it adjusts to pH 2-6.
上記塩化物としては塩化ナトリウム、塩化カリウム、塩化マグネシウム、塩化カルシウムなどが好ましい。これは、これらの塩化物が後の電解処理工程において殺菌作用の高い次亜塩素酸を発生させやすいからである。   As the chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride and the like are preferable. This is because these chlorides easily generate hypochlorous acid having a high bactericidal action in the subsequent electrolytic treatment process.
本発明において、余剰汚泥8への塩化物の添加量は0.1〜3質量%にするが、これは次の理由によるものである。すなわち、余剰汚泥8への塩化物の添加量が0.1質量%少ない場合は、電解処理時の電気抵抗が大きくなり、電力が熱エネルギーに使われて処理効率が低下する。そのため、処理時間を長くする必要があるが、処理時間を長くすると、死滅した微生物がさらに処理され、細胞壁が破壊される確率が高くなるため好ましくない。また、生成する次亜塩素酸の濃度が低くなるため、殺菌効果が少なくなって処理時間が長くなるため、電解槽を大きくすることが必要となり、システムの価格アップにつながるという問題もある。また、余剰汚泥8への塩化物の添加量が3質量%より多い場合は、殺菌(微生物の死滅)に必要な量よりはるかに多くの次亜塩素酸が発生し、塩化物が無駄になるだけでなく、ランニングコストのアップにつながる。また、電解処理が進みすぎる可能性が高くなり、そのため、細胞壁の破壊につながるおそれがある。従って、この塩化物の余剰汚泥への添加量としては、前記のように、0.1〜3質量%であることが必要であり、0.2〜0.8質量%が好ましい。   In the present invention, the amount of chloride added to the excess sludge 8 is 0.1 to 3% by mass, for the following reason. That is, when the amount of chloride added to the excess sludge 8 is 0.1% by mass, the electrical resistance during the electrolytic treatment increases, and electric power is used for thermal energy, resulting in a reduction in treatment efficiency. Therefore, it is necessary to lengthen the treatment time. However, if the treatment time is lengthened, the dead microorganisms are further treated, and the probability that the cell wall is destroyed is not preferable. In addition, since the concentration of hypochlorous acid produced is low, the sterilizing effect is reduced and the treatment time is extended, so that it is necessary to enlarge the electrolytic cell, leading to an increase in the price of the system. Further, when the amount of chloride added to the excess sludge 8 is more than 3% by mass, much more hypochlorous acid is generated than the amount necessary for sterilization (microbe kill), and the chloride is wasted. As well as increase running costs. In addition, there is a high possibility that the electrolytic treatment will proceed excessively, which may lead to the destruction of the cell wall. Accordingly, the amount of chloride added to the excess sludge needs to be 0.1 to 3% by mass, and preferably 0.2 to 0.8% by mass, as described above.
薬剤混合槽9において、余剰汚泥8に添加する酸は、殺菌作用(微生物の死滅作用)を高めるために添加するものであるが、この酸としては、例えば、塩酸や硫酸などの強酸が好ましい。そのほか、硝酸やリン酸などを用いることも考え得るが、これらは曝気槽に返送しさらに沈殿槽で濃縮汚泥と上澄液とに分離したときに上澄液に窒素化合物やリン化合物が含有される原因になる。また、酢酸などの有機酸は有機物を増加させることから好ましくない。そのため、環境に影響を与えずしかも比較的安価な塩酸や硫酸が好ましく、塩酸は次亜塩素酸の供給源にもなることから特に好ましい。   In the chemical mixing tank 9, the acid added to the excess sludge 8 is added to enhance the bactericidal action (microbe killing action). As this acid, for example, a strong acid such as hydrochloric acid or sulfuric acid is preferable. In addition, it is possible to use nitric acid, phosphoric acid, etc., but when these are returned to the aeration tank and further separated into concentrated sludge and supernatant in the sedimentation tank, the supernatant contains nitrogen compounds and phosphorus compounds. Cause. Also, organic acids such as acetic acid are not preferred because they increase organic matter. Therefore, hydrochloric acid and sulfuric acid that do not affect the environment and are relatively inexpensive are preferable, and hydrochloric acid is particularly preferable because it also serves as a source of hypochlorous acid.
本発明においては、上記のように余剰汚泥に酸を添加してpH2〜6に調整することによって発生した次亜塩素酸を効率よく存在させ、殺菌作用を向上させるが、このpHとしては特にpH4〜6が好ましい。pHが2より低い場合は有害な塩素ガスが発生し、細胞壁を傷つけ、pH6より高い場合は殺菌作用が低下する。また、アルカリ性にすると、殺菌作用が低下するだけでなく、不溶解性有機物の減少が激しくなり、電解処理前後での不溶解性有機物の減少率が25質量%を超えるようになって、それをそのまま曝気槽2に返送すると、曝気槽2での消化処理に際しての負荷の増加につながる。また、アルカリ性にすると、微生物の細胞壁が傷つけられやすく、プロテアーゼにより微生物内部から細胞壁を溶解させることができなくなり、不溶解性有機物を溶解性有機物に効率よく変えることができなくなる。   In the present invention, hypochlorous acid generated by adding acid to surplus sludge as described above and adjusting to pH 2 to 6 is efficiently present to improve the bactericidal action. ~ 6 is preferred. When the pH is lower than 2, harmful chlorine gas is generated, and the cell wall is damaged. When the pH is higher than 6, the bactericidal action is lowered. In addition, when it is made alkaline, not only the bactericidal action is lowered, but the decrease of insoluble organic matter becomes severe, and the reduction rate of insoluble organic matter before and after electrolytic treatment exceeds 25% by mass. If it returns to the aeration tank 2 as it is, it will lead to the increase in the load at the time of the digestion process in the aeration tank 2. If alkaline, the cell wall of the microorganism is easily damaged, the cell wall cannot be dissolved from the inside of the microorganism by protease, and the insoluble organic substance cannot be efficiently converted into the soluble organic substance.
さらに、これら電解処理後の汚泥を曝気槽に返送する際、曝気槽の環境を変化させないことが好ましく、曝気槽のpHは6〜7の間に保つことが好ましく、特に6.5〜7の間に保つことが好ましい。沈殿槽4では、重力沈降を利用した沈殿により、活性汚泥は約100倍に濃縮されるため、pHが4.5程度であれば、返送時にpHの調整は必要ないが、それより低い場合はアルカリにより汚泥のpHを4.5以上に調整する必要がある。   Further, when returning the sludge after the electrolytic treatment to the aeration tank, it is preferable not to change the environment of the aeration tank, and it is preferable to maintain the pH of the aeration tank between 6 and 7, particularly 6.5 to 7 It is preferable to keep it in between. In the sedimentation tank 4, since activated sludge is concentrated about 100 times by precipitation using gravity sedimentation, if the pH is about 4.5, it is not necessary to adjust the pH at the time of return, but if lower than that, It is necessary to adjust the pH of the sludge to 4.5 or more with alkali.
本発明では、薬剤混合槽9で薬剤(すなわち、塩化物と酸)が混合された余剰汚泥は薬剤混合汚泥10として電解槽11に導入され、その電解槽11において電解されることで、電極表面で生じる次亜塩素酸による殺菌が行われる。そして、この電解処理により殺菌された余剰汚泥は電解処理済汚泥12として曝気槽2に返送される。上記電解時の電流密度は大きいほど、電解時間が短くて済むが、電極間の電圧が上昇し水の分解も起こり殺菌効率を低下させるため、電流密度は1〜40mA/cmにすることが必要であり、3〜20mA/cmが好ましい。 In the present invention, surplus sludge mixed with chemicals (that is, chloride and acid) in the chemical mixing tank 9 is introduced into the electrolytic tank 11 as the chemical mixed sludge 10 and electrolyzed in the electrolytic tank 11, whereby the electrode surface Is sterilized with hypochlorous acid produced in Then, surplus sludge sterilized by this electrolytic treatment is returned to the aeration tank 2 as electrolytically treated sludge 12. The larger the current density at the time of electrolysis, the shorter the electrolysis time is. However, the voltage between the electrodes rises and water is decomposed to reduce the sterilization efficiency. Therefore, the current density should be 1 to 40 mA / cm 2. It is necessary and 3 to 20 mA / cm 2 is preferable.
また、電解に用いる電極の表面はアモルファスカーボン、グラファイトなどの炭素系材料で構成されていることが好ましい。電極に炭素系材料を用いることで、殺菌効率が向上し、かつ電極の消耗を少なくすることができる。   The surface of the electrode used for electrolysis is preferably composed of a carbon-based material such as amorphous carbon or graphite. By using a carbon-based material for the electrode, the sterilization efficiency can be improved and the consumption of the electrode can be reduced.
ただし、炭素系材料のみで電極を作製すると割れやすいため、チタン板やステンレス鋼板に上記炭素系材料をコーティングした電極を用いてもよいし、また、それらの炭素系材料の上にさらにダイヤモンドまたはダイヤモンドライクカーボンをコーティングした電極を用いてもよい。上記のダイヤモンドやダイヤモンドライクカーボンには導電性を付与するためにホウ素などをドープしておくことが好ましい。   However, if an electrode is made of only a carbon-based material, it is easy to break. Therefore, an electrode obtained by coating the above-mentioned carbon-based material on a titanium plate or stainless steel plate may be used. An electrode coated with like carbon may be used. The diamond or diamond-like carbon is preferably doped with boron or the like in order to impart conductivity.
電解用の電源は、直流電源が好ましく、その直流をそのまま用いてもよいが、その直流に一定時間毎に逆電圧を印加して用いることが好ましい。   The power source for electrolysis is preferably a direct current power source, and the direct current may be used as it is. However, it is preferable to apply a reverse voltage to the direct current at regular intervals.
これは電解が進行すると電極表面に金属などが析出して被膜を形成し、電極の表面を変質させて次亜塩素酸の生成効率を下げるため、逆電圧により金属被膜を酸化・脱落させるためである。上記逆電圧を印加する時間は60秒に1〜5秒が好ましい。逆電圧を印加する時間が1秒より短い場合は、金属被膜の酸化がほとんど起こらず、5秒より長くしてもそれに伴う効果の増加がなく、むしろ次亜塩素酸の生成効率を低下させるおそれがある。また、その逆電圧は1.5〜10Vが好ましく、特に2〜5Vが好ましい。上記逆電圧が1.5Vより低い場合は、電流が少なくなるため、金属を酸化する反応速度が遅くなる。また、逆電圧が10Vより高い場合は、電解速度が速くなり、ガス発生が多くなって次亜塩素酸の生成効率が低下して、殺菌効率を低下させる。   This is because, as electrolysis progresses, metal deposits on the electrode surface to form a coating, alters the surface of the electrode and lowers the production efficiency of hypochlorous acid, and oxidizes and drops the metal coating by reverse voltage. is there. The time for applying the reverse voltage is preferably 1 to 5 seconds in 60 seconds. When the time for applying the reverse voltage is shorter than 1 second, oxidation of the metal film hardly occurs, and even if it is longer than 5 seconds, there is no increase in the effect, and there is a possibility that the generation efficiency of hypochlorous acid is rather lowered. There is. The reverse voltage is preferably 1.5 to 10 V, particularly preferably 2 to 5 V. When the reverse voltage is lower than 1.5V, the current is reduced, so that the reaction rate for oxidizing the metal is slow. On the other hand, when the reverse voltage is higher than 10 V, the electrolysis rate is increased, the generation of gas is increased, the generation efficiency of hypochlorous acid is lowered, and the sterilization efficiency is lowered.
また、電解液量と電力との関係は0.2〜1Ah/lが好ましく、特に0.3〜0.7Ah/lが好ましい。電解液量に対する電力が0.2Ah/lより小さい場合は、次亜塩素酸の生成が少なくなって電解時間が長くなり、電解液量に対する電力が2Ah/lより大きい場合は、不溶解性有機物の減少が大きくなり、むしろ負荷が大きくなる原因になるおそれがある。   Further, the relationship between the amount of the electrolytic solution and the electric power is preferably 0.2 to 1 Ah / l, and particularly preferably 0.3 to 0.7 Ah / l. When the power with respect to the amount of electrolyte is less than 0.2 Ah / l, the generation of hypochlorous acid is reduced and the electrolysis time is prolonged, and when the power with respect to the amount of electrolyte is more than 2 Ah / l, insoluble organic matter There is a possibility that the decrease of the increase becomes larger and the load becomes larger.
また、電解時の汚泥の温度は10〜40℃が好ましい。温度が40℃より高い場合は、不溶解性有機物の量が全体の40質量%以上と多くなり、結果的に負荷を増加させ、また曝気槽に返送すると曝気槽の活性汚泥が一部死滅するため負荷が増加して好ましくない。また、温度が10℃より低い場合は、粘度の増加により、電解効率が低下するため同様に好ましくない。   Moreover, the temperature of the sludge at the time of electrolysis has preferable 10-40 degreeC. When the temperature is higher than 40 ° C., the amount of insoluble organic matter increases to 40% by mass or more of the whole, resulting in an increase in load, and when returned to the aeration tank, a part of the activated sludge in the aeration tank is killed. Therefore, the load increases, which is not preferable. Moreover, when temperature is lower than 10 degreeC, since electrolysis efficiency falls by the increase in a viscosity, it is not preferable similarly.
つぎに、実施例を挙げて本発明をより具体的に説明する。ただし、本発明はそれらの実施例に限定されるものではない。   Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
実施例1
pH6.7、BOD200mg/リットル、SS75mg/リットルの有機性汚水を曝気槽に導入し、上記有機性汚水を30℃で、8時間微生物処理して微生物により有機物の分解処理を行った。なお、上記曝気槽はオキシデーション・ディッチ槽である。
Example 1
Organic sewage having a pH of 6.7, BOD of 200 mg / liter and SS of 75 mg / liter was introduced into an aeration tank, and the organic sewage was subjected to microbial treatment at 30 ° C. for 8 hours to decompose organic matter with microorganisms. The aeration tank is an oxidation ditch tank.
上記のように曝気槽で微生物処理をして得られた活性汚泥含有液を沈殿槽に導入し、2時間放置して活性汚泥を沈殿させ、上澄液を処理済水として沈殿槽から放出し(この処理済水は殺菌処理して処理システム系外に放出される)、沈殿して濃度が高くなった汚泥を濃縮汚泥として沈殿槽から取り出した。この時の濃縮汚泥中の固形分濃度、すなわち、MLSSは11850mg/リットルであった。   The activated sludge-containing liquid obtained by microbial treatment in the aeration tank as described above is introduced into the precipitation tank, left for 2 hours to precipitate the activated sludge, and the supernatant liquid is discharged from the precipitation tank as treated water. (This treated water is sterilized and released to the outside of the treatment system), and the sludge that has been precipitated and has a high concentration was taken out from the sedimentation tank as a concentrated sludge. The solid content concentration in the concentrated sludge at this time, that is, MLSS was 11850 mg / liter.
上記濃縮汚泥のうちの25質量%相当量を曝気槽に戻し(この曝気槽へ戻す汚泥は「返送汚泥」と呼ばれる)、残りの75質量%を余剰汚泥として薬剤混合槽へ導入し、そこで、塩化ナトリウムを濃度が0.5質量%になるように余剰汚泥に添加し、また、塩酸を加えて余剰汚泥のpHを4.5に調整した。   25% by mass of the concentrated sludge is returned to the aeration tank (the sludge to be returned to the aeration tank is called “return sludge”), and the remaining 75% by mass is introduced into the chemical mixing tank as surplus sludge. Sodium chloride was added to the excess sludge so as to have a concentration of 0.5 mass%, and hydrochloric acid was added to adjust the pH of the excess sludge to 4.5.
そして、薬剤混合槽から取り出した薬剤混合汚泥は電解槽に送られ、そこで、電解して汚泥中の微生物の死滅化処理(殺菌処理)を行った。   And the chemical | medical agent mixing sludge taken out from the chemical | medical agent mixing tank was sent to the electrolysis tank, and it electrolyzed and killed the microorganisms in a sludge (sterilization process).
この電解処理について詳しく説明すると、電解槽の内容積は120リットルであり、電極は正極がアモルファスカーボン製で、負極も同様にアモルファスカーボン製であり、その有効面積は、正極、負極とも、10000cmであり、電流密度は8mA/cmであった。そして、薬剤混合汚泥、すなわち、電解に供される余剰汚泥の電解槽への流量は、80リットルであり、電解時の余剰汚泥の温度は30℃に保たれていて、電解時間は20分間であった。すなわち、電解処理にあたっての使用電力は電解液量に対して0.33Ah/lであった。そして、電極での次亜塩素酸と微生物との接触効率を上げ、ガス発生による汚泥の浮上を防止するため、振動型攪拌機を用いて攪拌した。 This electrolytic treatment will be described in detail. The electrolytic cell has an internal volume of 120 liters, the positive electrode is made of amorphous carbon, and the negative electrode is also made of amorphous carbon. The effective area of both the positive and negative electrodes is 10,000 cm 2. The current density was 8 mA / cm 2 . The flow rate of the chemical mixed sludge, that is, the surplus sludge used for electrolysis to the electrolytic cell is 80 liters, the temperature of the surplus sludge during electrolysis is kept at 30 ° C., and the electrolysis time is 20 minutes. there were. That is, the electric power used for the electrolytic treatment was 0.33 Ah / l with respect to the amount of the electrolytic solution. Then, in order to increase the contact efficiency between hypochlorous acid and microorganisms at the electrode and prevent the sludge from floating due to gas generation, stirring was performed using a vibration type stirrer.
この電解処理による微生物の死滅率、すなわち、殺菌率は98%以上であり、電解処理後の汚泥のMLSSは10430mg/リットルであった。電解処理によるMLSSの減少率は質量基準で約12%で、溶解性有機物STOCは15mg/リットルから490mg/リットルに増加した。上記のように、電解処理によりMLSSが11850mg/リットルから10430mg/リットルに減少したのは、電解処理により汚泥中の微生物の一部が、細胞壁が傷付けられてその内部の可溶性有機物が細胞壁外部に溶出したことによるものである。すなわち、電解処理により汚泥中の微生物は、細胞壁が傷付くことなく死滅して固形分として残るもの(このものは時間の経過に伴って曝気槽で可溶性有機物に変わる)と細胞壁が傷付けられて細胞壁内部の可溶性有機物が細胞壁外部に流出して細胞壁が主体になったものとに分かれ(このものは、その後も不溶解性有機物として残る)、電解処理直後においてはこの両者で固形物を構成し、細胞壁内部から外部へ溶出した可溶性有機物分などによってMLSSが減少する。   The killing rate of microorganisms by this electrolytic treatment, that is, the sterilization rate was 98% or more, and the MLSS of the sludge after electrolytic treatment was 10430 mg / liter. The reduction rate of MLSS due to the electrolytic treatment was about 12% on a mass basis, and the soluble organic matter STOC increased from 15 mg / liter to 490 mg / liter. As described above, MLSS decreased from 11850 mg / liter to 10430 mg / liter by electrolytic treatment. Some of the microorganisms in the sludge were damaged by electrolytic treatment, and soluble organic substances inside the cell elute out of the cell wall. It is because of having done. That is, the microorganisms in the sludge by the electrolytic treatment are killed without damaging the cell wall and remain as solids (this changes to soluble organic matter in the aeration tank over time) and the cell wall is damaged and the cell wall The internal soluble organic matter flows out of the cell wall and is divided into those mainly composed of the cell wall (this remains as an insoluble organic matter thereafter), and immediately after electrolytic treatment, both constitute a solid matter, MLSS is reduced by the soluble organic matter eluted from the cell wall to the outside.
前記の電解処理による殺菌率98%は次のようにして求めた。すなわち、電解処理後の汚泥に空気を10分間バブリングし、その溶存酸素の減少率の測定を行った。溶存酸素の減少率の測定に先立って、BOD200mg/リットル、SS75mg/リットルを含む有機性汚水(原水)を消化処理し、沈殿槽に搬入する直前の原水の溶存酸素の減少率から求めた殺菌率を0とし、蒸留水の溶存酸素の減少率(減少なし)から求めた殺菌率を100%とし、上記原水に対して、その20%を蒸留水で希釈した活性汚泥の殺菌率を20%とし、50%を蒸留水で希釈した活性汚泥の殺菌率を50%とし、70%を蒸留水で希釈した活性汚泥液の殺菌率を70%として検量線を引き、この検量線を用いて溶存酸素の減少率の測定結果を殺菌率として求めたところ、殺菌率は前記のように98%であった。また、電解処理前後の汚泥のMLSSは質量基準で約12%減少していた。   The sterilization rate of 98% by the electrolytic treatment was determined as follows. That is, air was bubbled through the sludge after electrolytic treatment for 10 minutes, and the reduction rate of the dissolved oxygen was measured. Prior to measurement of the rate of decrease in dissolved oxygen, organic sewage (raw water) containing BOD 200 mg / liter and SS 75 mg / liter was digested and the rate of sterilization determined from the rate of decrease in dissolved oxygen immediately before being brought into the settling tank The sterilization rate determined from the decrease rate of dissolved oxygen (no decrease) in distilled water is 100%, and the sterilization rate of activated sludge obtained by diluting 20% of the raw water with distilled water is 20%. The calibration curve was drawn with the sterilization rate of the activated sludge diluted with distilled water as 50% and the sterilization rate of the activated sludge solution diluted as 70% as distilled water as 70%. As a result, the sterilization rate was 98% as described above. Moreover, MLSS of the sludge before and behind the electrolytic treatment was reduced by about 12% on a mass basis.
そして、この電解処理後の汚泥を再び曝気槽に供給し、これを繰り返して余剰汚泥の削減を行った。この一連の処理を30日間連続して行った後(30日間処理後)の曝気槽中のMLSSは3200mg/リットルと安定し、沈殿槽で上澄み液として放出された処理済液(以下、「上澄み排水」という)の水質もpHが6.5、BODが5mg/リットル、SSが11mg/リットルと、本電解処理による余剰汚泥の削減システムを採用する以前の余剰汚泥を廃棄するプロセス時の上澄み排水の水質とほとんど変わらなかった。   And the sludge after this electrolytic treatment was again supplied to the aeration tank, and this was repeated, and the excess sludge was reduced. The MLSS in the aeration tank after performing this series of treatments for 30 consecutive days (after 30 days of treatment) was stabilized at 3200 mg / liter, and was treated as a supernatant liquid (hereinafter referred to as “supernatant” in the precipitation tank). The water quality of the wastewater) is pH 6.5, BOD 5 mg / liter, SS 11 mg / liter, and the wastewater in the process of discarding excess sludge before adopting the system for reducing excess sludge by this electrolytic treatment. The water quality was almost the same.
なお、上澄み排水の水質はpHが6〜8、BODが60mg/リットル以下、SSが120mg/リットル以下であることが必要であるが、上記のように実施例1の上澄み排水の水質はこの要求を充分に満足させることのできるものであった。   In addition, the water quality of the supernatant drainage is required to have a pH of 6 to 8, a BOD of 60 mg / liter or less, and an SS of 120 mg / liter or less. Can be satisfied sufficiently.
実施例2〜5および比較例1〜2
電解処理に供する余剰汚泥のpHを1.5(比較例1)、2.0(実施例2)、3.0(実施例3)、5.5(実施例4)、6.0(実施例5)、6.5(比較例2)に変化させた以外は、実施例1と同様に処理して余剰汚泥の削減を行い、電解処理による殺菌率とMLSSの減少率、30日間処理後の曝気槽中のMLSS量および上澄み排水の水質を実施例1と同様に調べた。なお、pHが3以下の場合は電解処理後、水酸化ナトリウムを添加してpHを4.5に戻した後に曝気槽に返送した。また、電解処理による余剰汚泥はMLSSが実験時に変化していくため、その減少率として評価した。電解処理に供する余剰汚泥のpHおよび電解処理による殺菌率とMLSSの減少率を表1に示し、30日間処理後の曝気槽中のMLSS量および上澄み排水のBOD量とSS量を表2に示す。
Examples 2-5 and Comparative Examples 1-2
The pH of the excess sludge to be subjected to the electrolytic treatment is 1.5 (Comparative Example 1), 2.0 (Example 2), 3.0 (Example 3), 5.5 (Example 4), 6.0 (Execution) Except for changing to Examples 5) and 6.5 (Comparative Example 2), the same treatment as in Example 1 was carried out to reduce excess sludge, and the sterilization rate by electrolytic treatment and the reduction rate of MLSS, after 30 days of treatment The amount of MLSS in the aeration tank and the quality of the supernatant drainage were examined in the same manner as in Example 1. In addition, when pH was 3 or less, after electrolytic treatment, sodium hydroxide was added, pH was returned to 4.5, and it returned to the aeration tank. Moreover, since the MLSS changes at the time of experiment, the excess sludge by electrolytic treatment was evaluated as the reduction rate. Table 1 shows the pH of the excess sludge to be subjected to electrolytic treatment, the sterilization rate by electrolytic treatment, and the reduction rate of MLSS, and Table 2 shows the MLSS amount in the aeration tank after 30 days treatment and the BOD amount and SS amount of the supernatant drainage. .
表1〜2に示す結果から明らかなように、電解処理に供する余剰汚泥のpHを2.0〜6.0の範囲内にした実施例2〜5では、電解処理による殺菌率が高く、またMLSSの減少率も24%以下と大きくなりすぎることなく、その結果、30日間処理後の曝気槽中のMLSS量が4000mg/l以下の範囲内にあって余剰汚泥を効率よくすることができ、かつ上澄み排水の水質もBODが37mg/l以下、SSが50mg/l以下と適正な範囲内に維持することができた。   As is clear from the results shown in Tables 1 and 2, in Examples 2 to 5 in which the pH of the excess sludge to be subjected to the electrolytic treatment is in the range of 2.0 to 6.0, the sterilization rate by the electrolytic treatment is high, The reduction rate of MLSS is not too large as 24% or less, and as a result, the amount of MLSS in the aeration tank after 30 days treatment is within the range of 4000 mg / l or less, and excess sludge can be made efficient. In addition, the water quality of the supernatant drainage was able to be maintained within an appropriate range with a BOD of 37 mg / l or less and an SS of 50 mg / l or less.
これに対して、pHを1.5にした比較例1では、電解処理によるMLSSの減少率が大きすぎるため、曝気槽での負荷が増大して、30日間処理後の曝気槽中のMLSS量が4800mg/リットルと4000mg/リットルを超えるため、一般に知られているように沈殿槽で分離がしにくくなり、上澄み排水の水質がBOD60mg/l、SS170mg/lと悪化した。そのため、適宜余剰汚泥を廃棄して水質の低下を防止する必要があった。また、pHを6.5にした比較例2では、電解処理による殺菌率が低くなり、その結果、曝気槽中のMLSS量が多くなり、それに伴って上澄み排水の水質もBODが120mg/l、SS280mg/lと低下した。   In contrast, in Comparative Example 1 in which the pH was 1.5, the MLSS reduction rate due to the electrolytic treatment was too large, so the load on the aeration tank increased, and the amount of MLSS in the aeration tank after 30 days treatment Since it exceeds 4800 mg / liter and 4000 mg / liter, it is difficult to separate in a sedimentation tank as is generally known, and the quality of the supernatant drainage water deteriorated to BOD 60 mg / l and SS 170 mg / l. For this reason, it was necessary to appropriately discard excess sludge to prevent deterioration of water quality. Moreover, in the comparative example 2 which made pH 6.5, the disinfection rate by an electrolysis process becomes low, As a result, the amount of MLSS in an aeration tank increases, and the water quality of a supernatant drainage is also BOD 120 mg / l in connection with it, It decreased to SS 280 mg / l.
実施例6〜11および比較例3〜4
電流密度および電解時間を変えた以外は、実施例1と同様に処理して余剰汚泥の削減を行った。その際の電流密度、電解時間などを表3に示し、上記削減処理の結果、すなわち、電解処理による殺菌率とMLSSの減少率、30日間処理後の曝気槽中のMLSS量および上澄み排水中のBOD量とSS量を表4に示す。
Examples 6-11 and Comparative Examples 3-4
Except for changing the current density and electrolysis time, the same treatment as in Example 1 was performed to reduce excess sludge. The current density and electrolysis time at that time are shown in Table 3. As a result of the above reduction treatment, that is, the sterilization rate and MLSS reduction rate by the electrolysis treatment, the amount of MLSS in the aeration tank after 30 days treatment, and the supernatant drainage Table 4 shows the BOD amount and SS amount.
表3〜表4に示す結果から明らかなように、電流密度を1〜40mA/cmの範囲内にした実施例6〜11では、電解処理による殺菌率が高く、またMLSSの減少率も高くなりすぎることなく、その結果、30日間処理後の曝気槽中のMLSS量も4000mg/l以下の範囲内にあって余剰汚泥の削減が効率よく行われており、また、その際の上澄み排水の水質もBODが35mg/l以下、SSが30mg/l以下と、適正な範囲内に維持されていた。 As is apparent from the results shown in Tables 3 to 4, in Examples 6 to 11 in which the current density is in the range of 1 to 40 mA / cm 2 , the sterilization rate by electrolytic treatment is high, and the reduction rate of MLSS is also high. As a result, the amount of MLSS in the aeration tank after the treatment for 30 days is also within the range of 4000 mg / l or less, and the excess sludge is efficiently reduced. The water quality was also maintained within an appropriate range with a BOD of 35 mg / l or less and an SS of 30 mg / l or less.
これに対して、電流密度が0.5mA/cmと小さい比較例3や電流密度が50mA/cmと大きい比較例4では、30日間処理後の曝気槽中のMLSSが多く、余剰汚泥の削減が充分ではなく、また上澄み排水の水質もBOD量が多く、適正な範囲内に維持することができなかった。 In contrast, the current density is in large Comparative Example 4 small Comparative Example 3 and the current density 0.5 mA / cm 2 is a 50 mA / cm 2, a number MLSS in the aeration tank after treatment for 30 days, the excess sludge Reduction was not sufficient, and the quality of the supernatant drainage water was large in BOD, and could not be maintained within an appropriate range.
実施例12〜14および比較例5〜6
塩化ナトリウムの添加量を変えた以外は、実施例1と同様に余剰汚泥の削減を行った。その際の電解処理の殺菌率とMLSSの減少率、30日間処理後の曝気槽中のMLSS量および上澄み排水中のBOD量とSS量をその塩化ナトリウムの添加量と共に表5に示す。
Examples 12-14 and Comparative Examples 5-6
Excess sludge was reduced in the same manner as in Example 1 except that the amount of sodium chloride added was changed. Table 5 shows the sterilization rate of the electrolytic treatment and the reduction rate of MLSS, the MLSS amount in the aeration tank after 30 days treatment, the BOD amount and SS amount in the supernatant drainage, together with the amount of sodium chloride added.
表5に示す結果から明らかなように、塩化ナトリウムの添加量を0.1〜3質量%の範囲内にした実施例12〜14では、電解処理による殺菌率が高く、またMLSSの減少率も大きくなりすぎることなく、その結果、30日間処理後の曝気槽中のMLSS量も4000mg/l以下の範囲内にあって余剰汚泥の削減が効率よく行われており、また、その際の上澄み排水の水質もBOD量が18mg/l以下、SS量が30mg/l以下と適正な範囲内に維持されていた。   As is apparent from the results shown in Table 5, in Examples 12 to 14 in which the amount of sodium chloride added was in the range of 0.1 to 3% by mass, the sterilization rate by electrolytic treatment was high, and the reduction rate of MLSS was also high. As a result, the amount of MLSS in the aeration tank after the treatment for 30 days is also within the range of 4000 mg / l or less, and the excess sludge is efficiently reduced. The water quality was maintained within a proper range with a BOD amount of 18 mg / l or less and an SS amount of 30 mg / l or less.
実施例15〜17
電解処理に供する余剰汚泥に添加する塩化物を実施例1の塩化ナトリウムから他の塩化物に変えた以外は、実施例1と同様に処理して余剰汚泥の削減を行った。その際の電解処理による殺菌率とMLSSの減少率、30日間処理後の曝気槽中のMLSS量および上澄み排水中のBOD量とSS量をその塩化物の種類と共に表6に示す。
Examples 15-17
Excess sludge was reduced by treating in the same manner as in Example 1 except that the chloride added to the excess sludge to be subjected to electrolytic treatment was changed from sodium chloride in Example 1 to other chlorides. Table 6 shows the sterilization rate and MLSS reduction rate by electrolytic treatment at that time, the MLSS amount in the aeration tank after 30 days treatment, and the BOD amount and SS amount in the supernatant drainage together with the type of chloride.
表6に示す結果から明らかなように、塩化物として、塩化カリウムを用いた実施例15、塩化カルシウムを用いた実施例16、塩化マグネシウムを用いた実施例17のいずれも、電解処理による殺菌率が高く、またMLSSの減少率が高すぎることなく、その結果、30日処理後の曝気槽中のMLSS量が4000mg/l以下の範囲内にあって余剰汚泥の削減が効率よく行われており、また、その際の上澄み排水の水質もBODが14mg/l以下、SSが16mg/l以下と適正な範囲内に維持されていた。   As is clear from the results shown in Table 6, the sterilization rate by electrolytic treatment in all of Example 15 using potassium chloride, Example 16 using calcium chloride, and Example 17 using magnesium chloride as chlorides. And the reduction rate of MLSS is not too high, and as a result, the amount of MLSS in the aeration tank after 30 days treatment is within the range of 4000 mg / l or less, and excess sludge is efficiently reduced. In addition, the water quality of the supernatant drainage at that time was maintained within an appropriate range with a BOD of 14 mg / l or less and an SS of 16 mg / l or less.
実施例18〜19
電極を正極および負極とも実施例1のアモルファスカーボンで構成したものからグラファイトで構成したものとチタン板上にコーティングしたグラファイト層上にさらにダイヤモンドライクカーボンをコーティングしたものに変えた以外は、実施例1と同様に処理して余剰汚泥の削減を行った。その際の電解処理による殺菌率とMLSSの減少率、30日間処理後の曝気槽中のMLSS量および上澄み排水中のBOD量とSS量をその電極表面の材料と共に表7に示す。
Examples 18-19
Example 1 except that both the positive electrode and the negative electrode were made of amorphous carbon in Example 1 instead of those made of graphite and those in which a graphite layer coated on a titanium plate was further coated with diamond-like carbon. In the same way, excess sludge was reduced. Table 7 shows the sterilization rate and MLSS reduction rate by electrolytic treatment at that time, the MLSS amount in the aeration tank after 30 days treatment, the BOD amount and SS amount in the supernatant drainage, together with the material on the electrode surface.
表7に示す結果から明らかなように、電極をグラファイトで構成した実施例18、電極をチタン板上にコーティングしたグラファイト層上にさらにダイヤモンドライクカーボンをコーティングして構成した実施例19とも、電解処理による殺菌率が高く、またMLSSの減少率も大きくなりすぎることなく、その結果、30日間処理後の曝気槽中のMLSS量も4000mg/l以下の範囲内にあって余剰汚泥の削減が効率よく行われており、また、その際の上澄み排水の水質もBODが17mg/l以下、SS量が16mg/l以下と適正な範囲内に維持されていた。   As is apparent from the results shown in Table 7, both the Example 18 in which the electrode was made of graphite and the Example 19 in which the electrode was further coated with diamond-like carbon on the graphite layer in which the electrode was coated on a titanium plate were subjected to electrolytic treatment. As a result, the amount of MLSS in the aeration tank after 30 days treatment is within the range of 4000 mg / l or less, and the excess sludge can be efficiently reduced. In addition, the quality of the supernatant drainage water at that time was maintained within an appropriate range with a BOD of 17 mg / l or less and an SS amount of 16 mg / l or less.
本発明に係る電解処理による余剰汚泥の削減システムの処理プロセスの概要を示す図である。It is a figure which shows the outline | summary of the process of the reduction system of the excess sludge by the electrolytic treatment which concerns on this invention.
符号の説明Explanation of symbols
1 有機性汚水
2 曝気槽
3 活性汚泥含有液
4 沈殿槽
5 処理済液
6 濃縮汚泥
7 返送汚泥
8 余剰汚泥
9 薬剤混合槽
10 薬剤混合汚泥
11 電解槽
12 電解処理済汚泥
DESCRIPTION OF SYMBOLS 1 Organic sewage 2 Aeration tank 3 Liquid containing activated sludge 4 Precipitation tank 5 Processed liquid 6 Concentrated sludge 7 Return sludge 8 Surplus sludge 9 Chemical mixing tank 10 Chemical mixing sludge 11 Electrolysis tank 12 Electrolyzed sludge

Claims (12)

  1. 有機性汚水の処理装置であって
    有機性汚水を微生物処理して活性汚泥含有水を得るための曝気槽と、
    上記曝気槽で得られた活性汚泥含有水を重力沈降法によって形分濃度が0.3〜2質量%になるように濃縮して濃縮汚泥と上澄液とに分離するための沈殿槽と、
    濃縮汚泥の一部を曝気槽に返送する機構と、
    残りの濃縮汚泥を余剰汚泥とし、その余剰汚泥に塩化物を0.1〜3質量%添加するとともに、酸を添加してpHを2〜6に調整する機構と、
    電極を備えており、上記余剰汚泥に1〜40mA/cmの電流密度で電解処理を施し、余剰汚泥中の微生物を殺菌するための電解槽と、
    上記電解処理した余剰汚泥を再び曝気槽に返送する機構
    を有することを特徴とする有機性汚水の処理装置
    A processing device organic sewage,
    An aeration tank for microbial treatment of organic wastewater to obtain water containing activated sludge ;
    The activated sludge containing water obtained in the above aeration tank, solid content concentration by gravity sedimentation method using an evaporator to 0.3 to 2 wt%, precipitation for separating the concentrated sludge and supernatant A tank,
    A mechanism for returning a portion of the concentrated sludge to the aeration tank ;
    The remaining concentrated sludge is used as excess sludge, and 0.1 to 3% by mass of chloride is added to the excess sludge, and an acid is added to adjust the pH to 2 to 6, and
    Includes an electrode, subjected to electrolysis at a current density of 1~40mA / cm 2 in the excess sludge, and electrolytic cell of order to sterilize microorganisms excess sludge,
    Mechanism for returning the above-mentioned electrolytically treated excess sludge to the aeration tank again
    And an organic sewage treatment apparatus .
  2. 塩化物として、塩化ナトリウム、塩化カリウム、塩化マグネシウム、または塩化カルシウムを添加し、として、硫酸または塩酸を添加するものであることを特徴とする請求項1記載の有機性汚水の処理装置The apparatus for treating organic sewage according to claim 1 , wherein sodium chloride, potassium chloride, magnesium chloride, or calcium chloride is added as a chloride , and sulfuric acid or hydrochloric acid is added as an acid.
  3. 電解槽の有する電極が、アモルファスカーボンもしくはグラファイトの炭素系材料からなるか、またはチタン板もしくはステンレス鋼板上に上記炭素系材料をコーティングしたものからなるか、または上記チタン板もしくはステンレス鋼板上に直接もしくは上記チタン板もしくはステンレス鋼板上にコーティングした上記炭素系材料上にダイヤモンドもしくはダイヤモンドライクカーボンをコーティングしたものからなることを特徴とする請求項1記載の有機性汚水の処理装置 The electrode of the electrolytic cell is made of a carbon-based material of amorphous carbon or graphite, or is formed by coating the carbon-based material on a titanium plate or a stainless steel plate, or directly or on the titanium plate or the stainless steel plate. 2. The organic sewage treatment apparatus according to claim 1, wherein said carbon-based material coated on said titanium plate or stainless steel plate is coated with diamond or diamond-like carbon.
  4. 電解処理に用いる電源が直流電源であって、その直流をそのまま用いるか、またはその直流に一定時間毎に逆電圧を印加して用いるものであることを特徴とする請求項1記載の有機性汚水の処理装置The power used in the electrolytic treatment is a DC power supply, as it is used, or organic sewage according to claim 1, characterized in that the use by applying a reverse voltage at regular intervals on the direct current that DC Processing equipment .
  5. 曝気槽がオキシデーション・ディッチであることを特徴とする請求項1記載の有機性汚水の処理装置The apparatus for treating organic sewage according to claim 1, wherein the aeration tank is an oxidation ditch.
  6. 有機性汚水の微生物処理により生じる余剰汚泥を削減するための処理方法であって、曝気槽で微生物処理された活性汚泥含有水を沈殿槽で重力沈降法によって活性汚泥中の固形分濃度が0.3〜2質量%になるように濃縮して濃縮汚泥と上澄液とに分離し、濃縮汚泥の一部を曝気槽に返送する第一工程、残りの濃縮汚泥を余剰汚泥とし、その余剰汚泥に塩化物を0.1〜3質量%添加するとともに、酸を添加してpH2〜6に調整する第二工程、電解槽中で電極を用いて上記余剰汚泥に1〜40mA/cmの電流密度で電解処理を施し、余剰汚泥中の微生物を殺菌する第三工程、上記電解処理した余剰汚泥を再び曝気槽に返送する第四工程を有し、電解処理により余剰汚泥を削減することを特徴とする有機性汚水の処理方法 A treatment method for reducing surplus sludge generated by microbial treatment of organic sludge, wherein the activated sludge-containing water that has been microbially treated in an aeration tank has a solid content concentration of 0. Concentrate to 3 to 2% by mass, separate into concentrated sludge and supernatant, and return part of the concentrated sludge to the aeration tank. The remaining concentrated sludge is used as excess sludge, and the excess sludge A second step of adding 0.1 to 3% by mass of chloride to the solution and adjusting the pH to 2 to 6 by adding an acid, and using an electrode in the electrolytic cell, an electric current of 1 to 40 mA / cm 2 in the excess sludge characterized in that the electrolytic processing on a density, a third step of sterilizing microorganisms excess sludge, have a fourth step of returning again aeration tank the excess sludge described above electrolytic treatment, to reduce the excess sludge by electrolysis Organic wastewater treatment method .
  7. 前記第二工程において、添加する塩化物が塩化ナトリウム、塩化カリウム、塩化マグネシウム、塩化カルシウムから選ばれ、酸が硫酸、塩酸から選ばれることを特徴とする請求項記載の有機性汚水の処理方法The method for treating organic sewage according to claim 6 , wherein in the second step, the chloride to be added is selected from sodium chloride, potassium chloride, magnesium chloride and calcium chloride, and the acid is selected from sulfuric acid and hydrochloric acid. .
  8. 前記第三工程において、電気分解に用いる電極がアモルファスカーボンもしくはグラファイトの炭素系材料からなるか、またはチタン板もしくはステンレス鋼板上に上記炭素系材料をコーティングしたものからなるか、または上記チタン板もしくはステンレス鋼板上に直接もしくは上記チタン板もしくはステンレス鋼上にコーティングした上記炭素系材料上にダイヤモンドもしくはダイヤモンドライクカーボンをコーティングしたものからなることを特徴とする請求項記載の有機性汚水の処理方法In the third step, the electrode used for the electrolysis is made of a carbon-based material of amorphous carbon or graphite, or is made of a titanium plate or a stainless steel plate coated with the carbon-based material, or the titanium plate or stainless steel 7. The method for treating organic sewage according to claim 6, wherein the carbon-based material coated directly on the steel plate or on the titanium plate or stainless steel is coated with diamond or diamond-like carbon.
  9. 前記第三工程において、電解処理する余剰汚泥を10〜40℃の範囲に保持することを特徴とする請求項記載の有機性汚水の処理方法The method for treating organic sewage according to claim 6 , wherein, in the third step, surplus sludge to be subjected to electrolytic treatment is maintained in a range of 10 to 40 ° C.
  10. 前記第三工程において、電解処理に用いる電源が直流電源であって、その直流をそのまま用いるか、またはその直流に一定時間毎に逆電圧を印加して用いることを特徴とする請求項記載の有機性汚水の処理方法In the third step, the power used in the electrolytic treatment is a DC power supply of claim 6, wherein the use by applying a reverse voltage at regular time intervals the DC or used as is or in DC Organic sewage treatment method .
  11. 前記第三工程において、電解処理前後で、余剰汚泥中の不溶解性有機物の含有量の減少率が25質量%以下であることを特徴とする請求項記載の有機性汚水の処理方法The method for treating organic sewage according to claim 6 , wherein, in the third step, the reduction rate of the content of the insoluble organic matter in the excess sludge is 25% by mass or less before and after the electrolytic treatment.
  12. 曝気槽がオキシデーション・ディッチであることを特徴とする請求項記載の有機性汚水の処理方法
    The method for treating organic sewage according to claim 6, wherein the aeration tank is an oxidation ditch.
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JP2007007546A (en) * 2005-06-30 2007-01-18 Hitachi Plant Technologies Ltd Sludge treatment method
JP4584173B2 (en) * 2006-03-29 2010-11-17 株式会社日立プラントテクノロジー Method for electrolytic treatment of excess sludge
JP2008049343A (en) * 2007-11-09 2008-03-06 Nishihara Environment Technology Inc Organic waste water treatment device
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Publication number Priority date Publication date Assignee Title
CN102765784A (en) * 2012-07-14 2012-11-07 江阴顶立环保科技有限公司 Electrolytic catalytic oxidation ditch
CN102765784B (en) * 2012-07-14 2013-11-27 江阴顶立环保科技有限公司 Electrolytic catalytic oxidation ditch

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