JP2018114465A - Biological treatment method of organic wastewater - Google Patents
Biological treatment method of organic wastewater Download PDFInfo
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- VSIIXMUUUJUKCM-UHFFFAOYSA-D pentacalcium;fluoride;triphosphate Chemical compound [F-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O VSIIXMUUUJUKCM-UHFFFAOYSA-D 0.000 description 1
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- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
-
- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Abstract
Description
本発明は、有機性廃水の生物処理方法に関する。 The present invention relates to a biological treatment method for organic wastewater.
出願人は、既に、活性汚泥法を利用した廃水の処理において、活性汚泥の可溶化処理工程を組み入れることで余剰汚泥の減量化を達成し、従来の処理方法に比較して最終段階で放流される処理水の悪化を生じさせることなく、設備の拡大や処理フローを複雑化させることなく、最終的に処理が必要となる汚泥の含水率を大幅に低減することで、汚泥処理にかかるコストを大幅に低減することが可能な、経済性に優れた、地球環境保護の点からも有用な有機性廃水の生物処理方法を提案している（特許文献１、２）。また、余剰汚泥を効率的に可溶化処理する方法についての提案もしている（特許文献３）。 The applicant has already achieved the reduction of excess sludge by incorporating the activated sludge solubilization process in the treatment of wastewater using the activated sludge method, and it is discharged at the final stage compared to the conventional treatment method. The cost of sludge treatment can be reduced by drastically reducing the moisture content of sludge that ultimately needs treatment without causing deterioration of treated water and without complicating the expansion of the equipment and the treatment flow. A biological treatment method of organic wastewater that can be significantly reduced and is economical and excellent in terms of protecting the global environment has been proposed (Patent Documents 1 and 2). Moreover, the proposal about the method of solubilizing an excess sludge efficiently is also made (patent document 3).
しかしながら、本発明者らの検討によれば、余剰汚泥を可溶化処理する工程を設けた有機性廃水の生物処理方法によって、余剰汚泥量を大幅に減量できるが、実際の有機性廃水の処理に適用した場合に、処理水のリン濃度が上昇する傾向があることがわかった。 However, according to the study by the present inventors, the amount of excess sludge can be greatly reduced by the biological treatment method of organic wastewater provided with a process for solubilizing excess sludge. When applied, it was found that the phosphorus concentration of the treated water tends to increase.
ここで、活性汚泥処理水のリン濃度削減の方法としては、活性汚泥の曝気槽あるいは最終沈殿池入口に、鉄塩溶液又はアルミニウム塩溶液等の金属化合物を添加して、リン酸イオンを難溶性のリン酸鉄あるいはリン酸アルミニウム等の金属化合物として活性汚泥中に固定し、余剰汚泥とともに系外に引き抜くことが行われている。 Here, as a method for reducing the phosphorus concentration of the activated sludge treated water, a metal compound such as an iron salt solution or an aluminum salt solution is added to the activated sludge aeration tank or the inlet of the final sedimentation basin to make phosphate ions sparingly soluble. It is fixed in activated sludge as a metal compound such as iron phosphate or aluminum phosphate, and is pulled out of the system together with excess sludge.
ところが、上記した余剰汚泥を可溶化処理する工程を設けた、余剰汚泥の排出量を削減あるいは排出しない運転を行う方法では、活性汚泥中に固定されたリンを系外に排出できないし、排出した場合は固定されたリンとともに活性汚泥も系外に引き抜いてしまうことになり、余剰汚泥削減の目的が達成できないことになる。 However, in the method of performing the operation that reduces or eliminates excess sludge discharge, provided with a process for solubilizing excess sludge as described above, phosphorus fixed in the activated sludge cannot be discharged out of the system and discharged. In this case, the activated sludge is also drawn out together with the fixed phosphorus, and the purpose of reducing excess sludge cannot be achieved.
したがって、本発明の目的は、余剰汚泥を可溶化処理する工程を設けた余剰汚泥量を簡便な方法で大幅に減量化させることが可能な、簡易且つ経済的な有機性廃水の処理方法において問題となる処理水のリン濃度が上昇する傾向を、簡便な方法で、効果的に抑制できる有機性廃水の生物処理方法を提供することにある。 Therefore, an object of the present invention is to provide a problem in a simple and economical method for treating organic wastewater that can significantly reduce the amount of excess sludge provided with a process for solubilizing excess sludge by a simple method. An object of the present invention is to provide a biological treatment method for organic wastewater that can effectively suppress the tendency of increasing the phosphorus concentration of treated water by a simple method.
上記の目的は、下記の本発明によって達成される。すなわち、本発明は、有機性廃水を、少なくとも、最初沈殿槽と、活性汚泥処理槽と、最終沈殿槽とを用いて行う活性汚泥処理方法において、最終沈殿槽で固液分離された余剰汚泥の一部又は全部を可溶化処理するための可溶化処理工程を設け、該可溶化処理工程で、汚泥を可溶化する処理中の汚泥に、あるいは、可溶化処理後の汚泥に、リン酸イオンを吸着及び／又は不溶化する物質を加えたのち、可溶化した汚泥を最初沈殿槽に戻すことを特徴とする有機性廃水の生物処理方法を提供する。 The above object is achieved by the present invention described below. That is, the present invention is an activated sludge treatment method in which organic waste water is used at least using a first sedimentation tank, an activated sludge treatment tank, and a final sedimentation tank. A solubilization treatment step for solubilizing a part or all of the solution is provided, and in the solubilization treatment step, phosphate ions are added to the sludge being solubilized or to the sludge after the solubilization treatment. Provided is a biological treatment method for organic wastewater, characterized in that after solubilizing and / or insolubilizing substances are added, the solubilized sludge is first returned to the settling tank.
本発明の有機性廃水の生物処理方法の好ましい形態としては、前記有機性廃水が、下水であること；前記リン酸イオンを吸着及び／又は不溶化する物質が、リン酸イオンと結合して不溶性あるいは難溶性の塩を形成する金属又は金属塩であること；前記リン酸イオンを吸着及び／又は不溶化する物質が、アルミニウム又は鉄及びこれらの塩からなる群から選ばれるいずれかであること、が挙げられる。 As a preferred form of the biological treatment method of the organic wastewater of the present invention, the organic wastewater is sewage; the substance that adsorbs and / or insolubilizes the phosphate ion is insoluble or bound to the phosphate ion. It is a metal or a metal salt that forms a hardly soluble salt; and the substance that adsorbs and / or insolubilizes the phosphate ions is any one selected from the group consisting of aluminum or iron and salts thereof. It is done.
本発明によれば、余剰汚泥を可溶化処理する工程を設けた余剰汚泥量を簡便な方法で大幅に減量化させることが可能な、簡易且つ経済的な有機性廃水の処理方法において、簡便な方法でありながら、処理水のリン濃度が上昇することを効果的に抑制できる有機性廃水の生物処理方法が提供される。 According to the present invention, in a simple and economical organic wastewater treatment method, the amount of surplus sludge provided with a step of solubilizing surplus sludge can be greatly reduced by a simple method. Although it is a method, the biological treatment method of the organic wastewater which can suppress effectively that the phosphorus concentration of treated water raises is provided.
以下、好ましい実施の形態を挙げて本発明を更に詳細に説明する。本発明者らは、前記した、余剰汚泥を可溶化処理する工程を設けた有機性廃水の生物処理方法を、下水等の実際の有機性廃水の処理に適用した場合に、処理水のリン濃度が上昇する原因について鋭意検討を行い、得られた知見に基づき更なる検討を行った結果、本発明に至った。 Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. When the above-described biological treatment method for organic wastewater provided with a step of solubilizing excess sludge is applied to the treatment of actual organic wastewater such as sewage, the present inventors have set the phosphorus concentration of the treated water. As a result of intensive investigations on the cause of the increase in the number of nuclei and further studies based on the obtained knowledge, the present invention has been achieved.
まず、上記処理において処理水のリン濃度が上昇する傾向がみられる理由は、下記のように考えられる。余剰汚泥を可溶化処理すると、汚泥中のリンも可溶化されるため、従来のように、可溶化処理した汚泥を最初沈殿槽に戻して処理すると、可溶化したリンが、例えば、処理対象である下水中に溶出し、その結果、最初沈殿槽出口の下水のリン濃度が上昇する。このため、リン濃度の高い下水が原水として活性汚泥処理槽（以下「曝気槽」とも呼ぶ。）に流入することになり、曝気槽の後の最終沈殿槽出口の処理水のリン濃度が上昇することになると考えられる。 First, the reason why the phosphorus concentration of the treated water tends to increase in the above treatment is considered as follows. When the excess sludge is solubilized, phosphorus in the sludge is also solubilized, so when the sludge solubilized is first returned to the settling tank and treated, the solubilized phosphorus is, for example, treated in the treatment object. It elutes into some sewage, and as a result, the phosphorus concentration of the sewage at the outlet of the first sedimentation tank increases. For this reason, sewage with high phosphorus concentration flows into the activated sludge treatment tank (hereinafter also referred to as “aeration tank”) as raw water, and the phosphorus concentration of the treated water at the final sedimentation tank outlet after the aeration tank increases. It is thought that it will be.
ここで、最終処理水のリン濃度の上昇を抑制する方法としては次に挙げるような方法がある。
１．曝気槽あるいは最終沈殿槽入口にアルミニウム塩等の金属化合物を添加して、リンを活性汚泥中に固定して、処理水のリン濃度の上昇を抑制する方法。
２．最初沈殿槽の入口にアルミニウム塩等の金属化合物を添加して、下水中のリンを金属塩として固定し、最初沈殿槽で沈降分離する方法。
Here, as a method for suppressing the increase in the phosphorus concentration of the final treated water, there are the following methods.
1. A method of suppressing an increase in the phosphorus concentration of treated water by adding a metal compound such as an aluminum salt to an aeration tank or a final sedimentation tank and fixing phosphorus in activated sludge.
2. A method in which a metal compound such as an aluminum salt is added to the inlet of the first sedimentation tank, phosphorus in the sewage is fixed as a metal salt, and the sedimentation is separated in the first sedimentation tank.
しかしながら、これらの方法では、下記のような課題がある。まず、上記した１．の方法の場合は、曝気槽の活性汚泥中にリンを固定したリン酸金属塩と水酸化金属が蓄積することになる。そして、系外へのリンの排出は、最終沈殿槽で固液分離された余剰汚泥中として排出される。そして、添加したアルミニウム塩等の金属の曝気槽への濃縮倍率は、曝気槽と最終沈殿槽に存在する全汚泥量を排泥量で除した倍率、すなわち、汚泥滞留時間（ＳＲＴ）と等しくなる。具体的には、アルミニウム元素換算で３ｍｇ／ｌ添加した場合、ＳＲＴが１５日では、４５ｍｇ／ｌのアルミニウムが曝気槽内に存在することになる。このため、下記に挙げる課題が生じる。 However, these methods have the following problems. First, the above-described 1. In the case of this method, metal phosphate and metal hydroxide in which phosphorus is fixed accumulate in the activated sludge of the aeration tank. And the discharge | release of the phosphorus outside a system is discharged | emitted as the excess sludge separated into solid and liquid by the final sedimentation tank. The concentration ratio of the added aluminum salt or the like to the aeration tank is equal to the ratio obtained by dividing the total sludge amount present in the aeration tank and the final sedimentation tank by the amount of discharged sludge, that is, sludge residence time (SRT). . Specifically, when 3 mg / l is added in terms of aluminum element, 45 mg / l of aluminum is present in the aeration tank when the SRT is 15 days. For this reason, the following problems arise.
第一に、このリンを固定した金属塩と水酸化金属が蓄積した汚泥を可溶化処理すると、可溶化処理によって金属が再溶解することになる。この結果、可溶化処理に要する電力あるいは薬剤の必要量が大幅に増加し、可溶化処理に要するコストアップの大きな要因になる。また、第二に、アルミニウム等の金属は活性汚泥としては不活性である上、活性汚泥微生物の活性を阻害する可能性もある。 First, when the metal salt in which phosphorus is fixed and sludge in which metal hydroxide is accumulated are solubilized, the metal is re-dissolved by the solubilization process. As a result, the amount of electric power or chemicals required for the solubilization process is greatly increased, which is a major factor in increasing the cost required for the solubilization process. Second, metals such as aluminum are inactive as activated sludge and may inhibit the activity of activated sludge microorganisms.
前記した２．の方法の場合は、下記の課題がある。この方法では、最初沈殿槽入口でのリンの濃度(量)を正確に把握しながら、金属塩等の注入量等を制御しなければならない。しかし、最初沈殿槽に流入する下水の量並びにリンの濃度は１日の間でも大きく変動し、また、可溶化処理した汚泥の量も常に一定とは限らず、間欠的に排出されるケースの方が多く、リンの濃度(量)を正確に把握することは難しい。そして、リンの濃度(量)を正確に把握できないと、下記の課題が生じる。すなわち、正確なリンの濃度(量)を把握せずに、金属塩等を定量で注入すると金属塩の過不足が起こり、適正にリンを除去することができなくなる。まず、不足する場合は、処理水のリン濃度を抑えることができない。一方、過剰であれば、コストの問題もさることながら、曝気槽の活性汚泥に必要なリンが不足し、健全な活性汚泥が育たず、廃水処理に支障をきたすことになる。 2. As described above. In the case of this method, there are the following problems. In this method, it is necessary to control the injection amount of the metal salt and the like while accurately grasping the concentration (amount) of phosphorus at the beginning of the precipitation tank. However, the amount of sewage that flows into the settling tank and the concentration of phosphorus greatly fluctuate even during the day, and the amount of sludge that has been solubilized is not always constant and is discharged intermittently. There are many, and it is difficult to grasp the concentration (amount) of phosphorus accurately. If the concentration (amount) of phosphorus cannot be accurately grasped, the following problems arise. That is, if a metal salt or the like is injected quantitatively without knowing the exact phosphorus concentration (amount), the metal salt becomes excessive and insufficient, and phosphorus cannot be removed properly. First, when it is insufficient, the phosphorus concentration of treated water cannot be suppressed. On the other hand, if it is excessive, in addition to the problem of cost, phosphorus necessary for the activated sludge in the aeration tank will be insufficient, and healthy activated sludge will not grow, which will hinder wastewater treatment.
また、最初沈殿槽に流入する廃水は有機物濃度が高いため、有機物が金属とリンの反応を阻害するため、曝気槽ないし最終沈殿槽で添加する場合よりも金属塩等の添加量が多くなるという問題もある。 In addition, since the wastewater that flows into the first settling tank has a high organic matter concentration, the organic matter inhibits the reaction between the metal and phosphorus, so the amount of metal salt added is higher than when added in the aeration tank or the final settling tank. There is also a problem.
前記した１．の、リンを活性汚泥中に固定して、処理水のリン濃度の上昇を抑制する方法は、上記したように、汚泥を可溶化処理する工程を有する有機性廃水の生物処理方法においては不向きである。また、前記したように、２．の、下水中のリンを金属塩として固定し、最初沈殿槽で沈降分離する方法は、金属塩等の添加量が多くなることに加え、リンの濃度(量)を正確に把握が難しく、リン濃度が変動する実際の下水等に適用することは実際的でない。 As described above. The method of fixing phosphorus in activated sludge and suppressing the increase in the concentration of phosphorus in treated water is not suitable for the biological treatment method of organic wastewater having a step of solubilizing sludge as described above. is there. As described above, 2. In this method, the phosphorus in the sewage is fixed as a metal salt and settled and separated in the initial sedimentation tank. In addition to the increase in the amount of metal salt added, it is difficult to accurately determine the concentration (amount) of phosphorus. It is not practical to apply it to actual sewage whose concentration varies.
上記した課題に対し、本発明者らは鋭意検討した結果、最終沈殿槽で固液分離された余剰汚泥の一部又は全部を可溶化処理するための可溶化処理工程で、汚泥を可溶化する処理中の汚泥に、あるいは、可溶化処理後の汚泥に、リン酸イオンを吸着及び／又は不溶化する物質を加えたのち、可溶化した汚泥を最初沈殿槽に戻すという簡便な構成によって、上記した課題が一挙に解決できることを見出して本発明に至った。 As a result of diligent study on the above-described problems, the present inventors have solubilized sludge in a solubilization treatment step for solubilizing a part or all of the excess sludge separated into solid and liquid in the final sedimentation tank. By adding a substance that adsorbs and / or insolubilizes phosphate ions to the sludge being treated or to the sludge after the solubilization treatment, the solubilized sludge is first returned to the settling tank as described above. The inventors have found that the problems can be solved at once, and have reached the present invention.
上記のように構成したことで、本発明の処理方法によれば、汚泥の可溶化処理工程を有するにもかかわらず、処理水中のリン濃度の向上を確実に抑制することができる。本発明の処理方法では、汚泥を可溶化する処理中の汚泥に、あるいは、可溶化処理後の汚泥に、リン酸イオンを吸着及び／又は不溶化する物質を添加する構成としているため、前記した１．の処理方法の場合のように、リンを固定した金属塩と水酸化金属を可溶化することにならないので、可溶化処理に要する電力あるいは薬剤の必要量が大幅に増加することがない。 By having comprised as mentioned above, according to the processing method of this invention, although it has the sludge solubilization process process, the improvement of the phosphorus density | concentration in treated water can be suppressed reliably. In the treatment method of the present invention, since a substance that adsorbs and / or insolubilizes phosphate ions is added to the sludge being solubilized or to the sludge after the solubilization treatment, the above-mentioned 1 . As in the case of this treatment method, the metal salt and phosphorus hydroxide fixed with phosphorus are not solubilized, so that the power required for the solubilization treatment or the required amount of chemicals does not increase significantly.
更に、本発明の方法は、リン酸イオンを吸着及び／又は不溶化する物質を加えた可溶化した汚泥を最初沈殿槽に戻す構成としているため、上記物質でリンを固定したリン酸金属塩等は、最初沈殿槽から出る初沈汚泥に含まれて系外に除かれるので、リンを固定するためのアルミニウム等の金属が曝気槽に導入されることを防止できる。この結果、前記した１．の方法で懸念された、活性汚泥微生物の活性を阻害することが生じない。また、可溶化処理した汚泥に対してリン酸イオンを吸着及び／又は不溶化する物質を加えているので、例え、添加する物質に過不足があったとしても、曝気槽における処理対象である下水等のリン分を固定して除去するものではないので、前記した２．の方法で懸念される問題も生じない。 Furthermore, since the method of the present invention is configured so that the solubilized sludge to which a substance that adsorbs and / or insolubilizes phosphate ions is added is first returned to the settling tank, the metal phosphate, etc., in which phosphorus is fixed with the above substance, Since it is contained in the first settling sludge that comes out of the first settling tank and removed outside the system, it is possible to prevent the introduction of a metal such as aluminum for fixing phosphorus into the aeration tank. As a result, the aforementioned 1. Inhibiting the activity of activated sludge microorganisms, which was a concern in this method, does not occur. Moreover, since a substance that adsorbs and / or insolubilizes phosphate ions is added to the solubilized sludge, even if there is an excess or deficiency in the substance to be added, sewage, etc., to be treated in the aeration tank The phosphorus content is not fixed and removed. There is no problem with this method.
上記したように、本発明の方法では、リン酸イオンを吸着及び／又は不溶化する物質を加えた可溶化した汚泥を最初沈殿槽に戻すことで、上記物質でリンを固定したリン酸金属塩等を最初沈殿槽から出る初沈汚泥に含まれて系外に除かれる構成としているが、その際に、図３に示したように構成することも本発明の好ましい形態である。すなわち、図３に示した形態では、最初沈殿槽からの沈殿物を初沈汚泥濃縮槽で濃縮後、濃縮した汚泥を嫌気性消化装置に導入し、嫌気性消化法（メタン発酵法）で処理して、濃縮汚泥中の有機性の固形物を分解してメタンガスにし、液分を返流水として流入水とともに最初沈殿槽へ導入して、曝気槽で処理するように構成する。汚泥は脱水装置で脱水して脱水ケーキとする。このように構成することで、原水中の有機性固形物がより多く生物分解処理でき、その効率を高めることができると同時に、脱水ケーキの量を低減することができる。 As described above, in the method of the present invention, a solubilized sludge added with a substance that adsorbs and / or insolubilizes phosphate ions is first returned to the settling tank, so that a metal phosphate salt in which phosphorus is fixed with the above substance, etc. Is included in the first settling sludge that is first discharged from the settling tank and removed from the system. In this case, a configuration as shown in FIG. 3 is also a preferred embodiment of the present invention. That is, in the form shown in FIG. 3, after the sediment from the first sedimentation tank is concentrated in the primary sedimentation tank, the concentrated sludge is introduced into an anaerobic digester and treated by an anaerobic digestion method (methane fermentation method). Then, the organic solid matter in the concentrated sludge is decomposed into methane gas, and the liquid component is first introduced into the settling tank together with the inflowing water as return water, and is processed in the aeration tank. Sludge is dehydrated with a dehydrator to make a dehydrated cake. By comprising in this way, more organic solid substance in raw | natural water can be biodegraded, the efficiency can be raised, and the quantity of dehydration cake can be reduced simultaneously.
本発明の方法で使用するリン酸イオンを吸着及び／又は不溶化する物質としては、下記のものが挙げられる。まず、リン酸イオンを不溶化あるいは難溶化する、金属あるいは金属塩としては、鉄、アルミニウム、亜鉛、カルシウム、マグネシウム、及びこれらの金属塩が挙げられる。より具体的には、硫酸鉄、ポリ硫酸鉄、塩化アルミニウム、ポリ塩化アルミニウム、硫酸アルミニウム、アルミン酸ソーダ、塩化亜鉛、塩化カルシウム、水酸化カルシウム、硫酸マグネシウム、塩化マグネシウム及び水酸化マグネシウム等が挙げられる。 Examples of substances that adsorb and / or insolubilize phosphate ions used in the method of the present invention include the following. First, examples of the metal or metal salt that makes phosphate ion insoluble or hardly soluble include iron, aluminum, zinc, calcium, magnesium, and metal salts thereof. More specifically, iron sulfate, poly iron sulfate, aluminum chloride, poly aluminum chloride, aluminum sulfate, sodium aluminate, zinc chloride, calcium chloride, calcium hydroxide, magnesium sulfate, magnesium chloride, magnesium hydroxide and the like can be mentioned. .
また、リン酸イオンを吸着及び／又は固定化する物質としては、ゼオライト、カルシウムアパタイト、ハイドロタルサイト等が挙げられる。 Examples of substances that adsorb and / or fix phosphate ions include zeolite, calcium apatite, hydrotalcite, and the like.
本発明の方法を構成する余剰汚泥の可溶化処理工程における可溶化の方法としては、従来公知のいずれの方法も用いることができる。汚泥の可溶化の方法としては、例えば、下記の方法等を挙げることができる。
（１）鉄塩と過酸化水素によるＯＨラジカル酸化による可溶化
（２）オゾン酸化による可溶化
（３）超音波による物理的破壊による可溶化
（４）ビーズミル等による機械的なすり潰し／破壊による可溶化
（５）塩素での酸化による可溶化
（６）アルカリによる可溶化
（７）酸による可溶化
（８）５０〜９０℃に加熱して可溶化
（９）高温高圧下で可溶化
Any conventionally known method can be used as the solubilization method in the solubilization process of excess sludge constituting the method of the present invention. Examples of sludge solubilization methods include the following methods.
(1) Solubilization by OH radical oxidation with iron salt and hydrogen peroxide (2) Solubilization by ozone oxidation (3) Solubilization by physical destruction by ultrasonic waves (4) Possible by mechanical grinding / destruction by bead mill etc. Solubilization (5) Solubilization by oxidation with chlorine (6) Solubilization by alkali (7) Solubilization by acid (8) Solubilization by heating to 50-90 ° C (9) Solubilization under high temperature and high pressure
実施例と比較例を挙げて本発明を具体的に説明する。これらの実施例によって本発明が限定されるものではない。以下、％とあるのは、特に断りのない限り、質量基準である。 The present invention will be specifically described with reference to examples and comparative examples. The present invention is not limited by these examples. Hereinafter, “%” is based on mass unless otherwise specified.
（実施例１）
本実施例では、図１に示したベンチプラントによる実験を行った。処理フローの概略としては、余剰汚泥の一部を可溶化し、残りの余剰汚泥は、初沈汚泥とともに脱水処理し、可溶化処理した汚泥にリン酸イオンを吸着及び／又は不溶化する物質を添加した。
Example 1
In this example, the bench plant experiment shown in FIG. 1 was performed. As an outline of the treatment flow, a part of the excess sludge is solubilized, and the remaining excess sludge is dehydrated together with the primary sedimentation sludge, and a substance that adsorbs and / or insolubilizes phosphate ions is added to the solubilized sludge. did.
具体的には、下記のように処理した。処理する廃水として下水を用い、処理量５００Ｌ／日を２４時間均等かつ連続で処理を行った。図４に示したように、廃水を、まず、容量１００Ｌの最初沈殿槽でＳＳ分を沈降分離し、その後、容積２５０Ｌの曝気槽で活性汚泥処理を行い、容量２００Ｌの最終沈殿槽で、活性汚泥と処理水を固液分離した。固液分離した処理水は放流し、沈降した活性汚泥は、返送汚泥として１５０Ｌ／日を曝気槽に戻した。返送汚泥量の３．５％に相当する５．２５Ｌ／日を返送汚泥から分岐して、容積２Ｌの可溶化処理装置に送り、可溶化処理した。 Specifically, the treatment was as follows. Sewage was used as the wastewater to be treated, and a treatment amount of 500 L / day was treated uniformly and continuously for 24 hours. As shown in FIG. 4, the wastewater is first separated and separated from the SS in a first sedimentation tank having a capacity of 100 L, and then activated sludge treatment is performed in an aeration tank having a capacity of 250 L, and activated in a final sedimentation tank having a capacity of 200 L. Sludge and treated water were separated into solid and liquid. The treated water that had been separated into solid and liquid was discharged, and the activated sludge that had settled was returned to the aeration tank at 150 L / day as return sludge. 5.25 L / day corresponding to 3.5% of the amount of returned sludge was branched from the returned sludge and sent to a solubilizing apparatus having a volume of 2 L for solubilization.
本実施例では、可溶化処理した処理後の汚泥に、ポリ塩化アルミニウム（ＰＡＣ）をアルミニウム原子換算で連続的に１ｇ／日添加した後、流入廃水と混合して最初沈殿槽に戻した。曝気槽のＭＬＳＳは１，８００ｍｇ／ｌを維持するように、適宜に余剰汚泥を引き抜いた。可溶化処理装置での汚泥の可溶化処理は、硫酸でｐＨ３に調整し、過酸化水素を、被処理汚泥の乾物換算量に対し５％添加して行った。 In this example, polyaluminum chloride (PAC) was continuously added at 1 g / day in terms of aluminum atoms to the sludge after the solubilization treatment, and then mixed with the influent wastewater and returned to the initial sedimentation tank. The excess sludge was appropriately extracted so that the MLSS of the aeration tank was maintained at 1,800 mg / l. The sludge solubilization treatment in the solubilization treatment apparatus was carried out by adjusting the pH to 3 with sulfuric acid and adding 5% of hydrogen peroxide to the dry matter equivalent of the treated sludge.
（実施例２）
実施例１の処理で用いたと同じ規模の、図２に示したベンチプラントで、実施例１と同じ下水を原水として、具体的には図５に示したようにして有機性廃水の処理を行った。本実施例では、可溶化処理装置に送る汚泥量を、返送汚泥量の５％に相当する７．５Ｌとした。また、曝気槽のＭＬＳＳを１，８００ｍｇ／ｌに維持するため、可溶化処理装置に送る汚泥量を変化させてＭＬＳＳを１，８００ｍｇ／ｌに調整し、余剰汚泥としての排泥は行わなかった。上記した以外は、実施例１の処理方法と同一条件で廃水処理をした。可溶化処理汚泥に添加したＰＡＣも、実施例１と同じ１ｇ／日とした。
(Example 2)
In the bench plant shown in FIG. 2 having the same scale as that used in the processing of Example 1, the same sewage as in Example 1 is used as raw water, and specifically, organic wastewater is processed as shown in FIG. It was. In this example, the amount of sludge to be sent to the solubilization apparatus was 7.5 L corresponding to 5% of the amount of returned sludge. In addition, in order to maintain the MLSS of the aeration tank at 1,800 mg / l, the amount of sludge sent to the solubilization treatment apparatus was changed to adjust the MLSS to 1,800 mg / l, and no excess sludge was discharged. . Except for the above, wastewater treatment was performed under the same conditions as in the treatment method of Example 1. The PAC added to the solubilized sludge was also 1 g / day as in Example 1.
（比較例１）
本比較例では、図６に示したようにして、実施例と同じ下水を原水として処理した。具体的には、実施例２の条件を、ＰＡＣの添加位置のみ最終沈殿槽の入り口に変更した以外は、ＰＡＣの添加量、可溶化処理条件を含め、その他の条件はすべて実施例２で行ったと同様にして廃水処理を行った。
(Comparative Example 1)
In this comparative example, as shown in FIG. 6, the same sewage as in the example was treated as raw water. Specifically, all the other conditions including the amount of PAC addition and the solubilization treatment conditions were performed in Example 2 except that the conditions of Example 2 were changed to the entrance of the final precipitation tank only at the PAC addition position. Wastewater treatment was carried out in the same manner as described above.
（比較例２）
本比較例では、図７に示したようにして、実施例と同じ下水を原水として処理した。具体的には、比較例１の処理システムから可溶化処理装置を無くし、他の処理条件は、比較例１で行った処理と全く同じ条件で廃水処理を行った。
(Comparative Example 2)
In this comparative example, as shown in FIG. 7, the same sewage as in the example was treated as raw water. Specifically, the solubilization processing apparatus was removed from the treatment system of Comparative Example 1, and the other treatment conditions were the same as those in Comparative Example 1, and the wastewater treatment was performed.
（実施例１、２及び比較例１、２の処理による処理結果）
以上で行った実施例１、実施例２、比較例１及び比較例２のそれぞれの処理方法を同時に３ヶ月間運転した。そして、後半の２ヶ月間の平均水質並びに脱水ケーキの日平均発生量（乾燥汚泥量換算）を測定し、その結果を表１にまとめて示した。
(Processing result by processing of Examples 1 and 2 and Comparative Examples 1 and 2)
The treatment methods of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 performed above were simultaneously operated for 3 months. And the average water quality for the latter two months and the daily average amount of dehydrated cake (in terms of dry sludge amount) were measured, and the results are summarized in Table 1.
表１に示したように、処理水の水質は、ＳＳ並びにＢＯＤについては、実施例及び比較例とも２ｍｇ／ｌ以下であり、総リンについては、いずれも１ｍｇ／ｌ以下と、良好な結果が得られた。また、処理水の総窒素については大きな差は無く、１１〜１５ｍｇ／ｌであった。また、脱水ケーキの発生量（乾燥汚泥ベース）については、実施例２の処理方法の場合が６９ｇ／日と、最も発生量が少なく、最も発生量が多かった、汚泥の可溶化工程のない比較例２の処理方法の場合の９２ｇ／日に対して、２５％削減された。同様に、実施例１の処理方法の場合についても、７５ｇ／日であり、比較例２の処理方法の場合に比べて１８．５％減となった。 As shown in Table 1, the quality of the treated water was 2 mg / l or less for both SS and BOD in both the examples and the comparative examples, and the total phosphorus was 1 mg / l or less, and good results were obtained. Obtained. Moreover, there was no big difference about the total nitrogen of treated water, and it was 11-15 mg / l. The amount of dehydrated cake generated (dry sludge base) is 69 g / day in the case of the treatment method of Example 2, which is the least generated amount and the most generated amount, without the sludge solubilization process. Compared to 92 g / day in the case of the processing method of Example 2, the reduction was 25%. Similarly, in the case of the processing method of Example 1, it was 75 g / day, which was 18.5% lower than that of the processing method of Comparative Example 2.
比較例１の処理方法の場合は、可溶化した汚泥量は実施例２の処理方法の場合と同じであるにもかかわらず、脱水ケーキの発生量は実施例２より多い７４ｇ／日となり、可溶化汚泥量の少ない実施例１とほぼ同じ値となった。この原因は定かではないが、表１に示したＭＬＳＳ中のアルミニウム含有量が異なることから、アルミニウム含有量が影響した可能性が推察される。すなわち、本発明者らは、可溶化処理過程で汚泥中に含まれるアルミニウムが、可溶化剤の反応に影響を与えたのではないかと推察している。実施例及び比較例のいずれの処理条件の場合も、アルミニウムの添加量は同一としていたのに対し、ＭＬＳＳ中のアルミニウム濃度は、実施例１及び実施例２の処理の場合は、いずれもＭＬＳＳ中のアルミニウム含有量が０．１％と少なかった。これに対し、例えば、比較例１の処理の場合は、ＭＬＳＳ中のアルミニウム含有量が１．４％であり、実施例１の１４倍の濃度を示すことがわかった。また、汚泥の可溶化工程を設けず、最終沈殿槽への導入経路でＰＡＣを添加した比較例２の方法でも、ＭＬＳＳ中のアルミニウム含有量が実施例の１７倍の濃度を示し、いずれの方法も、曝気槽での活性汚泥微生物の活性を阻害することが懸念された。これらのことから、本発明の実施例の、汚泥の可溶化工程を設け、且つ、可溶化した汚泥にＰＡＣ等のリン酸イオンを吸着及び／又は不溶化する物質を加えることの有用性が確認された。 In the case of the treatment method of Comparative Example 1, the amount of sludge solubilized was the same as in the case of the treatment method of Example 2, but the amount of dehydrated cake generated was 74 g / day, which was higher than that in Example 2, and allowed. It became substantially the same value as Example 1 with little amount of solubilized sludge. Although this cause is not certain, since the aluminum content in MLSS shown in Table 1 differs, it is guessed that the aluminum content may have influenced. That is, the present inventors presume that the aluminum contained in the sludge during the solubilization process may have affected the reaction of the solubilizer. In any of the processing conditions of the example and the comparative example, the aluminum addition amount was the same, whereas the aluminum concentration in MLSS was in MLSS in the case of the processing of Example 1 and Example 2. The aluminum content was as low as 0.1%. On the other hand, for example, in the case of the treatment of Comparative Example 1, it was found that the aluminum content in MLSS was 1.4%, indicating a concentration 14 times that of Example 1. Further, even in the method of Comparative Example 2 in which the PAC was added by the introduction route to the final sedimentation tank without providing the sludge solubilization step, the aluminum content in MLSS showed a concentration 17 times that of the Example, In addition, there was concern about inhibiting the activity of activated sludge microorganisms in the aeration tank. From these, the usefulness of adding a substance that adsorbs and / or insolubilizes phosphate ions such as PAC to the solubilized sludge is confirmed in the embodiment of the present invention. It was.
（実施例３）
本実施例では、実際の下水処理施設に本発明の処理方法を適用して実施し、その効果について確認した。具体的には、図８に示した処理槽の構成で、実施例２と同様に余剰汚泥としての排泥は行わずに処理した。この処理施設は、計画流入水量７，０００ｍ3／日で、本発明の処理方法を適用して３ヶ月実施した期間の平均流入水量は５，６００ｍ3／日であった。図８に示したように、廃水は、まず、容量５００ｍ3の最初沈殿槽でＳＳ分を沈降分離し、容積２，５００ｍ3の曝気槽で活性汚泥処理を行なった。この曝気槽は、直列４槽に区切られ嫌気好気法で運転されていた。容量１，５００ｍ3の最終沈殿槽で、活性汚泥と処理水を固液分離し、処理水は放流し、沈降した活性汚泥は返送汚泥として平均流量１９５ｍ3／日を曝気槽に戻した。
(Example 3)
In this example, the treatment method of the present invention was applied to an actual sewage treatment facility, and the effect was confirmed. Specifically, in the configuration of the treatment tank shown in FIG. 8, the treatment was performed without discharging the excess sludge as in Example 2. This treatment facility had a planned influent water volume of 7,000 m 3 / day, and an average inflow water quantity of 5,600 m 3 / day during a period of three months when the treatment method of the present invention was applied. As shown in FIG. 8, the waste water is first separated by sedimentation the SS component in the first precipitation tank of capacity 500 meters 3, it was subjected to activated sludge treatment in the aeration tank volume 2,500 m 3. This aeration tank was divided into four tanks in series and operated by an anaerobic aerobic method. In the final sedimentation tank with a capacity of 1,500 m 3 , the activated sludge and the treated water were solid-liquid separated, the treated water was discharged, and the precipitated activated sludge was returned to the aeration tank with an average flow rate of 195 m 3 / day.
返送汚泥量の約５．１％に相当する１０ｍ3／日を返送汚泥から分岐して可溶化処理装置に送り、可溶化処理した。可溶化処理した汚泥にアルミン酸ソーダをアルミニウム原子換算で連続的に１２ｋｇ／日添加した後、流入廃水と混合して最初沈殿槽に戻した。曝気槽のＭＬＳＳは１，８００〜２，２００ｍｇ／ｌに維持されていた。ＭＬＳＳを下げる場合は、可溶化処理装置での処理汚泥量を増やし、逆に上げる場合は処理汚泥量を減らすことで調整し、余剰汚泥の排泥は行わなかった。可溶化処理装置では苛性ソーダでｐＨ１０に調整し、酸素酸系酸化剤を被処理汚泥の乾物換算量に対し１％添加して、汚泥を可溶化した。最初沈殿槽から排泥される初沈汚泥は、重力濃縮後脱水処理されている。本実施例で実施した１ヶ月間の処理後の平均水質並びに脱水ケーキの日平均発生量（乾燥汚泥量換算）を表２に示した。 10 m 3 / day corresponding to about 5.1% of the amount of returned sludge was branched from the returned sludge and sent to a solubilizing apparatus to be solubilized. After 12 kg / day of sodium aluminate was continuously added to the solubilized sludge in terms of aluminum atoms, it was mixed with the influent wastewater and returned to the first sedimentation tank. The MLSS of the aeration tank was maintained at 1,800-2,200 mg / l. When MLSS was lowered, the amount of treated sludge in the solubilization treatment apparatus was increased, and when it was raised, adjustment was made by reducing the amount of treated sludge, and excess sludge was not discharged. In the solubilizer, the pH was adjusted to 10 with caustic soda, and 1% of an oxygen acid oxidizer was added to the dry matter equivalent of the treated sludge to solubilize the sludge. The first settling sludge discharged from the first settling tank is dewatered after gravity concentration. Table 2 shows the average water quality after one month of treatment carried out in this example and the daily average amount of dehydrated cake (in terms of dry sludge amount).
（比較例３）
表２中に、比較例３として、同じ下水処理場で本実施例の適用試験を行う前年の１年間の水質分析結果と、汚泥発生量とＭＬＳＳ中のアルミニウム濃度を示した。なお、比較例３では処理水のリン対策として、最終沈殿槽の流入部分にＰＡＣをアルミニウム原子換算で２〜３ｍｇ／ｌを連続的に注入していた。
(Comparative Example 3)
In Table 2, as Comparative Example 3, the water quality analysis results for the previous year in which the application test of this example was performed at the same sewage treatment plant, the sludge generation amount, and the aluminum concentration in MLSS are shown. In Comparative Example 3, as a countermeasure against phosphorus in the treated water, PAC was continuously injected into the inflow portion of the final sedimentation tank at 2 to 3 mg / l in terms of aluminum atoms.
表２に示したように、実施例３及び比較例３の方法とも、処理水の水質は、ＳＳ並びにＢＯＤは２ｍｇ／ｌ以下であり、また、総リンについても１ｍｇ／ｌ以下であり、いずれも良好な結果であった。総窒素についても、実施例３の方法の場合が３．２ｍｇ／ｌで、比較例３の方法の場合が３．５ｍｇ／ｌと、いずれも良好な結果であった。これに対し、脱水ケーキの発生量（乾燥汚泥ベース）では、実施例３の方法の場合が６９０ｋｇ／日であったのに対し、比較例３の方法の場合は８８５ｋｇ／日であり、実施例３の脱水ケーキ量が２０％以上少なく、汚泥量の削減効果も認められた。ＭＬＳＳ中のアルミニウム濃度は、実施例３の方法の場合が０．２％であったのに対し、比較例３の方法の場合は１．５％であり、実施例３の方法の場合の方が低濃度であることが確認された。 As shown in Table 2, in both the methods of Example 3 and Comparative Example 3, the quality of the treated water was SS and BOD of 2 mg / l or less, and the total phosphorus was 1 mg / l or less. Also good results. The total nitrogen was 3.2 mg / l for the method of Example 3 and 3.5 mg / l for the method of Comparative Example 3, both of which were good results. In contrast, the amount of dehydrated cake generated (dry sludge base) was 690 kg / day for the method of Example 3, whereas it was 885 kg / day for the method of Comparative Example 3. The amount of dehydrated cake of No. 3 was less than 20%, and a sludge reduction effect was also observed. The aluminum concentration in MLSS was 0.2% in the case of the method of Example 3, whereas it was 1.5% in the case of the method of Comparative Example 3, which was the case of the method of Example 3. Was confirmed to be a low concentration.
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