JP2004113917A

JP2004113917A - Treatment method for sludge of septic tank

Info

Publication number: JP2004113917A
Application number: JP2002280097A
Authority: JP
Inventors: Yutaka Yamada; 山田　豊; Seiji Izumi; 和泉　清司; Taichi Kamisaka; 上坂　太一; Tatsuya Uejima; 上島　達也
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 2002-09-26
Filing date: 2002-09-26
Publication date: 2004-04-15
Anticipated expiration: 2022-09-26
Also published as: JP4004370B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method for the sludge of a septic tank, performed by remodeling an existing excretion treatment plant interfering with operation by a change in the quality of raw water due to an increase in the feed-in quantity of the sludge of the septic tank and a reduction in excretion. <P>SOLUTION: The sludge of the septic tank is subjected to biological dentrification treatment in a membrane separation activated sludge tank and the excess sludge thereof is reduced in volume by methane fermentation in a membrane separation methane fermentation tank. The nitrogen component flowing out of the excess sludge at the time of methane fermentation is treated in the membrane separation activated sludge tank to realize both of water treatment (especially removal of nitrogen) of the sludge of the septic tank and the volume reduction of sludge at the same time. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は浄化槽汚泥の処理方法に関し、浄化槽汚泥の急増に悩む既設し尿処理場を改造する技術に係るものである。
【０００２】
【従来の技術】
この種の先行技術文献としては例えば特許文献１もしくは特許文献２がある。
【０００３】
【特許文献１】特開平７−６８２９４号公報
【０００４】
【特許文献２】特開平１１−１９７６３６号公報
ところで、我が国において下水道が整備されるまでの過渡的な生活排水処理として位置付けられてきた浄化槽は日本独特のものであるが今は世界でも注目される技術となっている。
【０００５】
近年浄化槽法が改正になり、風呂・台所・洗濯排水などの生活雑排水を垂れ流しにし、トイレの水洗排水だけを処理していた単独浄化槽は製造禁止となった。このため、トイレ水洗排水と生活雑排水の両方、即ち家庭から出る生活排水の全てを処理する合併処理浄化槽だけが製造・設置されるようになった。この合併処理浄化槽は恒久的な生活排水処理施設（３０年）として位置付けられているので、財政難に悩む地方自治体が下水による水洗化事業から浄化槽による水洗化事業へ切り替えるケースが増えるものと考えられる。
【０００６】
一般的な浄化槽のしくみは、生活排水中の汚物を微生物が食べることで排水を浄化し、沈殿槽で微生物を沈降させて分離し、その上澄み液を処理水として減菌後に放流している。微生物は排水を処理すればするほどにどんどん増殖して沈殿槽での固液分離に支障をきたすので、定期的に余剰汚泥としてバキューム車で引き抜いて最終的にし尿処理場に搬入して処理している。
【０００７】
水洗排水だけ処理する単独浄化槽に比べて合併処理浄化槽は余剰汚泥の発生量が多くなる。このため、近年し尿処理場に搬入される浄化槽汚泥量は増加傾向にあり、一部の処理場では計画処理量をオーバーし、処理場の運転に支障をきたしているところが出ている。さらに、下水や浄化槽などの水洗化人口の増加に伴って汲み取り人口が減少を続けているために、し尿処理場に搬入されるし尿と浄化槽汚泥の比率が建設当時とは逆転した比率となって原水の水質が変化したことがし尿処理場の運転を困難にしている一因である。
【０００８】
【発明が解決しようとする課題】
図４は２０年以上前（昭和５０年以前）に建設された代表的なし尿処理場における嫌気性消化方式もしくは好気性消化方式によるし尿処理方法を示すものである。
【０００９】
嫌気性消化方式では搬送車両１によって搬入する汲み取りし尿２と浄化槽３の嫌気性浄化槽汚泥４とを消化槽（嫌気性消化槽）５で約３０日間嫌気性細菌によってし尿中の汚物をメタンガスなどに分解処理（ＢＯＤ除去率８０％以上）しており、消化槽（嫌気性消化槽）５から出た脱離液を希釈水で２０倍に希釈して曝気槽等で活性汚泥処理６し、さらに減菌した後に放流していた。好気性消化方式では消化槽（好気性消化槽）５で１０日間以上好気性細菌によって汚物を炭酸ガスなどに分解し、沈殿分離後に上澄み液を２０倍に希釈して活性汚泥処理していた。
【００１０】
嫌気性消化方式、好気性消化方式は窒素除去の必要性が高まった昭和５５年以降はほとんど建設されることがなくなったが、いまだ更新されていない嫌気性消化方式、好気性消化方式の処理場が全国に約１２００箇所も残っている。
【００１１】
この浄化槽汚泥はもともと排水処理に寄与した微生物の集まりであるが、汚泥貯留槽などに長時間嫌気性で貯留されることにより腐敗して水中に有機汚濁物質や窒素などを放出する。したがって、そのままでは放流できず再処理が必要となる。
【００１２】
【表１】

ところで、表１に示すように、浄化槽汚泥は浮遊性物質（ＳＳ）を固液分離するだけで有機汚濁物質の指標であるＢＯＤやＣＯＤが８０〜９０％除去される。これに対してし尿は溶解性の有機汚濁物質がほとんどの割合を占める。
【００１３】
嫌気性消化方式や好気性消化方式はもともと高濃度の工場排水やし尿などに広く用いられている処理法であり、浄化槽汚泥の比率が高くなった場合には適当な処理方法とは言い難い。
【００１４】
図５は現在の浄化槽汚泥専用処理方法を示すものである。この方法では浄化槽１１から搬送車両１２によって搬入する浄化槽汚泥１３に含まれた夾雑物を夾雑物除去装置１４において除去し、夾雑物除去後の汚泥に凝集剤１５を添加して固液分離装置１６で固形物を除去した後に曝気槽等の活性汚泥処理１７し、沈殿槽１８で固液分離して分離した汚泥を余剰汚泥として取り出すとともに、一部を活性汚泥処理１７に返送し、分離した上澄み水を処理水として滅菌した後に放流している。
【００１５】
本発明は上記した課題を解決するものであり、浄化槽汚泥の搬入量の増加及びし尿減少により原水の水質変化により運転に支障をきたしている既設し尿処理場を改造して行う浄化槽汚泥の処理方法を提供することを目的とする。
【００１６】
【課題を解決するための手段】
上記課題を解決するために、請求項１に係る本発明の浄化槽汚泥の処理方法は、浄化槽汚泥を膜分離活性汚泥槽で生物学的脱窒素処理し、その余剰汚泥を膜分離メタン発酵槽でメタン発酵により減容化し、膜分離メタン発酵槽の膜分離水を膜分離活性汚泥槽で生物学的脱窒素処理するものである。
【００１７】
請求項２に係る本発明の浄化槽汚泥の処理方法は、浄化槽汚泥とし尿が搬入されるし尿処理施設において、浄化槽汚泥は膜分離活性汚泥槽で生物学的脱窒素処理し、膜分離活性汚泥槽の余剰汚泥とし尿とを混合して膜分離メタン発酵槽でメタン発酵させ、膜分離メタン発酵槽の膜透過水を活性汚泥処理するものである。
【００１８】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。図１において、浄化槽汚泥２１は搬送車両２２で処理施設に搬入し、搬入した浄化槽汚泥２１を夾雑物除去後に膜分離活性汚泥槽２３で生物学的脱窒素処理する。膜分離活性汚泥槽２３は硝化槽、脱窒槽、膜分離装置等で構成するものであり、ここでは一般的に公知のものを使用しており、浄化槽汚泥２１を生物学的脱窒素処理して膜分離で膜分離水と活性汚泥とに分離し、膜分離水を処理水として取り出して直接に放流する。
【００１９】
膜分離活性汚泥槽２３の余剰汚泥は膜分離メタン発酵槽２４へ投入する。膜分離メタン発酵槽２４はメタン発酵槽と膜分離装置等で構成するものであり、ここでは一般的に公知のものを使用しており、余剰汚泥をメタン発酵により減容化し、メタン発酵消化液の膜分離水を膜分離活性汚泥槽２３に戻す。
【００２０】
余剰汚泥をメタン発酵させると汚泥が嫌気性細菌に分解されて減容化するが汚泥中の窒素分がメタン発酵消化液中に溶解する。このため、メタン発酵槽のメタン発酵消化液を膜分離装置で分離した際に膜透過水に窒素分が混入するので、このままでは放流できない。そこで、膜透過水を膜分離活性汚泥槽２３に返送して窒素除去を行う。
【００２１】
このように浄化槽汚泥２１を膜分離活性汚泥槽２３と膜分離メタン発酵槽２４を組み合わせて処理し、膜分離活性汚泥槽２３の余剰汚泥を膜分離メタン発酵槽２４で減容化してメタン発酵の際に余剰汚泥から流出した窒素分を膜分離活性汚泥槽２３で処理することで、浄化槽汚泥の水処理（特に窒素除去）と汚泥の減容化の双方を同時に実現でき、系外へは膜分離活性汚泥槽２３の膜透過水としてそのまま放流することができる。しかも、膜分離活性汚泥槽２３、膜分離メタン発酵槽２４のそれぞれにおいて膜で固液分離することにより、槽外への微生物の流出がなくなって各槽で微生物濃度を高濃度に保持できるので、処理時間の短縮ができ、かつ槽容量もコンパクトにすることができる。
【００２２】
図２に示すように、浄化槽汚泥３１と汲取りし尿３２が搬入される嫌気性消化方式のし尿処理施設にあっては、既設の嫌気性消化槽に新たに膜分離装置を付設して膜分離メタン発酵槽３３に改造するとともに、生物学的脱窒素処理を行う膜分離活性汚泥槽３４を新設し、既設の活性汚泥処理設備３５を使用することで、本発明の浄化槽汚泥の処理方法を実現可能である。
【００２３】
この構成において、浄化槽汚泥３１は膜分離活性汚泥槽３４で生物学的脱窒素処理し、膜分離活性汚泥槽３４の余剰汚泥と汲取りし尿３２とを混合して膜分離メタン発酵槽３３でメタン発酵させ、膜分離メタン発酵槽３３の膜透過水を既設の活性汚泥処理設備３５で処理する。
【００２４】
これまでは処理施設全体を更新する必要があり、全面更新の場合には工期に２〜３ヵ年を要したが、本発明の浄化槽汚泥の処理方法を採用することで、安価な費用、短期間でしかも既設の施設を稼動させながら簡単に改造することができる。
【００２５】
図３に示すように、既設の活性汚泥処理設備３５を膜分離活性汚泥槽３６に改造し、その余剰汚泥を膜分離メタン発酵槽３３へ返送することも可能である。
【００２６】
【発明の効果】
以上のように本発明によれば、膜分離活性汚泥槽と膜分離メタン発酵槽とを組み合わせることにより、余剰汚泥の減容化とメタン発酵の際に汚泥分解に伴って溶出する窒素分の除去とを行うことができ、膜分離メタン発酵槽ではメタン菌を高濃度で維持できるようになり、従来の１／２〜１／３の処理時間で有機物分解率が４０％以上可能となった。既設の嫌気性し尿処理場においては、本発明の浄化槽処理方法を採用することにより安価な改造費で実現でき、浄化槽汚泥の増加とし尿処理施設の老朽化に悩む自治体にとってメリットがある。
【００２７】
膜分離活性汚泥槽の採用で、シンプルな処理フロー（図２参照）での処理が可能となり、運転管理が容易となった。また活性汚泥槽の大きさが従来の１／２から１／３の水槽容量で処理できるようになり、コンパクトな処理施設となる。
【図面の簡単な説明】
【図１】本発明の実施の形態における浄化槽汚泥の処理方法を示すフローシート図である。
【図２】本発明の他の実施の形態における浄化槽汚泥の処理方法を示すフローシート図である。
【図３】本発明の他の実施の形態における浄化槽汚泥の処理方法を示すフローシート図である。
【図４】従来のし尿処理方法を示すフローシート図である。
【図５】従来の浄化槽汚泥専用処理方法を示すフローシート図である。
【符号の説明】
２１　　浄化槽汚泥
２２　　搬送車両
２３　　膜分離活性汚泥槽
２４　　膜分離メタン発酵槽[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating septic tank sludge, and relates to a technique for remodeling an existing urine treatment plant suffering from a rapid increase in septic tank sludge.
[0002]
[Prior art]
Patent Documents 1 and 2 are examples of such prior art documents.
[0003]
[Patent Document 1] JP-A-7-68294
[Patent Document 2] Japanese Patent Application Laid-Open No. 11-197636 By the way, the septic tank which has been positioned as a transitional domestic wastewater treatment in Japan until the sewerage system is developed is unique to Japan, but is now attracting attention worldwide. Technology.
[0005]
In recent years, the Septic Tanks Law has been amended, and the production of single septic tanks, which only drain household wastewater such as baths, kitchens, and laundry drainage, and treat only toilet flush water, has been banned. For this reason, only combined treatment septic tanks that treat both toilet flush water and household wastewater, that is, all domestic wastewater from homes, have been manufactured and installed. Since the merged treatment septic tank is positioned as a permanent domestic wastewater treatment facility (30 years), it is likely that local governments suffering from financial difficulties will switch from the sewage flushing business to the septic tank flushing business. .
[0006]
In general, a septic tank is structured such that microorganisms eat filth in domestic wastewater to purify wastewater, sediment and separate the microorganisms in a sedimentation tank, and discharge the supernatant as treated water after sterilization. Microorganisms grow more and more as the wastewater is treated, which hinders solid-liquid separation in the sedimentation tank.Therefore, the microorganisms are periodically pulled out as excess sludge with a vacuum truck and finally transported to a human waste treatment plant for treatment. ing.
[0007]
As compared with a single septic tank that only treats washing water, the combined septic tank generates a larger amount of excess sludge. For this reason, the amount of septic tank sludge brought into the night soil treatment plant has been increasing in recent years, and some treatment plants have exceeded the planned treatment amount, which has hindered the operation of the treatment plant. In addition, the ratio of human waste and septic tank sludge brought into the night soil treatment plant has reversed the ratio at the time of construction, as the population of people pumping into the night soil treatment plant has been decreasing due to the increase in the number of people washed with sewage and septic tanks. Changes in the quality of the raw water are one of the factors that make it difficult to operate a urine treatment plant.
[0008]
[Problems to be solved by the invention]
FIG. 4 shows a method of treating human waste by an anaerobic digestion method or an aerobic digestion method in a typical human waste treatment plant constructed more than 20 years ago (before 1975).
[0009]
In the anaerobic digestion method, the collected urine 2 carried by the transport vehicle 1 and the anaerobic septic tank sludge 4 in the septic tank 3 are digested by anaerobic bacteria in a digestion tank (anaerobic digestion tank) 5 for about 30 days to convert filth in the urine into methane gas or the like. Decomposition treatment (BOD removal rate of 80% or more) is performed, the desorbed liquid discharged from digestion tank (anaerobic digestion tank) 5 is diluted 20 times with dilution water, and activated sludge treatment 6 is performed in an aeration tank and the like. It was released after sterilization. In the aerobic digestion method, a waste is decomposed into carbon dioxide gas or the like by an aerobic bacterium in a digestion tank (aerobic digestion tank) 5 for 10 days or more, and after sedimentation and separation, the supernatant is diluted 20-fold and activated sludge treatment is performed.
[0010]
Anaerobic digestion and aerobic digestion have almost never been constructed since 1980, when the need for nitrogen removal increased, but anaerobic digestion and aerobic digestion treatment plants that have not been updated yet However, there are about 1200 locations nationwide.
[0011]
This septic tank sludge is a collection of microorganisms that originally contributed to the wastewater treatment, but rots by being stored anaerobically for a long time in a sludge storage tank or the like, and rots to release organic pollutants and nitrogen into water. Therefore, it cannot be discharged as it is and requires reprocessing.
[0012]
[Table 1]

By the way, as shown in Table 1, septic tank sludge removes 80 to 90% of BOD and COD, which are indicators of organic pollutants, only by solid-liquid separation of suspended solids (SS). Human waste, on the other hand, is mostly composed of soluble organic pollutants.
[0013]
The anaerobic digestion system and the aerobic digestion system are originally widely used for high-concentration factory wastewater and human waste, and are not appropriate when the ratio of septic tank sludge increases.
[0014]
FIG. 5 shows a current treatment method exclusively for septic tank sludge. In this method, impurities contained in a septic tank sludge 13 carried in by a transport vehicle 12 from a septic tank 11 are removed in a contaminant removing device 14, and a flocculant 15 is added to the sludge from which the contaminants have been removed to form a solid-liquid separating device 16. Activated sludge treatment 17 such as an aeration tank is performed after removing solids, and sludge separated by solid-liquid separation in a sedimentation tank 18 is taken out as surplus sludge, and a part of the sludge is returned to the activated sludge treatment 17 to separate the supernatant. Water is sterilized as water and then released.
[0015]
The present invention solves the above-mentioned problems, and a method for treating septic tank sludge by remodeling an existing wastewater treatment plant that is hindering operation due to an increase in the amount of septic tank sludge carried in and a change in raw water quality due to a decrease in human waste. The purpose is to provide.
[0016]
[Means for Solving the Problems]
In order to solve the above problems, a method for treating a septic tank sludge according to the present invention according to claim 1 is to subject the septic tank sludge to biological denitrification in a membrane separation activated sludge tank, and to process the excess sludge in a membrane separation methane fermentation tank. The volume is reduced by methane fermentation, and the membrane separation water in the membrane separation methane fermentation tank is subjected to biological denitrification in a membrane separation activated sludge tank.
[0017]
According to the method for treating septic tank sludge of the present invention according to claim 2, in a human waste treatment facility into which urine is introduced as septic tank sludge, the septic tank sludge is subjected to biological denitrification in a membrane separation activated sludge tank, and the membrane separation activated sludge tank is treated. The surplus sludge and urine are mixed and subjected to methane fermentation in a membrane separation methane fermentation tank, and the membrane permeated water in the membrane separation methane fermentation tank is treated with activated sludge.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a septic tank sludge 21 is carried into a treatment facility by a transport vehicle 22, and the carried septic tank sludge 21 is subjected to biological denitrification in a membrane separation activated sludge tank 23 after removing impurities. The membrane separation activated sludge tank 23 is constituted by a nitrification tank, a denitrification tank, a membrane separation device and the like. Here, a generally known one is used, and the septic tank sludge 21 is subjected to a biological denitrification treatment. The membrane separation water and activated sludge are separated by membrane separation, and the membrane separation water is taken out as treated water and discharged directly.
[0019]
Excess sludge in the membrane separation activated sludge tank 23 is supplied to the membrane separation methane fermentation tank 24. The membrane separation methane fermentation tank 24 is composed of a methane fermentation tank, a membrane separation device, and the like. Here, a generally known one is used. Is returned to the membrane separation activated sludge tank 23.
[0020]
When excess sludge is subjected to methane fermentation, the sludge is decomposed into anaerobic bacteria to reduce the volume, but the nitrogen content in the sludge is dissolved in the methane fermentation digested liquid. For this reason, when the methane fermentation digested liquid in the methane fermentation tank is separated by the membrane separation device, nitrogen is mixed into the membrane permeated water, so that it cannot be discharged as it is. Then, the membrane permeated water is returned to the membrane separation activated sludge tank 23 to remove nitrogen.
[0021]
As described above, the septic tank sludge 21 is treated by combining the membrane separation activated sludge tank 23 and the membrane separation methane fermentation tank 24, and the excess sludge in the membrane separation activated sludge tank 23 is reduced in the membrane separation methane fermentation tank 24 to reduce the volume of methane fermentation. By treating the nitrogen content flowing out of the excess sludge in the membrane separation activated sludge tank 23, both water treatment (particularly nitrogen removal) of the septic tank sludge and volume reduction of the sludge can be realized at the same time. It can be discharged as it is as the permeated water of the separation activated sludge tank 23. Moreover, since the solid-liquid separation is performed by the membrane in each of the membrane separation activated sludge tank 23 and the membrane separation methane fermentation tank 24, the outflow of the microorganisms to the outside of the tank is eliminated, and the microorganism concentration can be maintained at a high concentration in each tank. The processing time can be reduced, and the capacity of the tank can be reduced.
[0022]
As shown in FIG. 2, in an anaerobic digestion type human waste treatment facility into which septic tank sludge 31 and pumped urine 32 are carried in, a new membrane separation device is attached to the existing anaerobic digestion tank. The method for treating septic tank sludge of the present invention is realized by remodeling into a methane fermentation tank 33 and newly installing a membrane separation activated sludge tank 34 for performing biological denitrification and using an existing activated sludge treatment facility 35. It is possible.
[0023]
In this configuration, the septic tank sludge 31 is subjected to biological denitrification in a membrane separation activated sludge tank 34, mixed with excess sludge from the membrane separation activated sludge tank 34 and the urine 32, and mixed with methane in a membrane separation methane fermentation tank 33. Fermentation is performed, and the permeated water of the membrane separation methane fermentation tank 33 is treated by the existing activated sludge treatment equipment 35.
[0024]
Until now, the entire treatment facility had to be renewed, and in the case of full renewal, the construction period required two to three years. However, adopting the septic tank sludge treatment method of the present invention provides low cost and short term. In addition, it can be easily modified while operating existing facilities.
[0025]
As shown in FIG. 3, the existing activated sludge treatment equipment 35 can be converted into a membrane separation activated sludge tank 36, and the surplus sludge can be returned to the membrane separation methane fermentation tank 33.
[0026]
【The invention's effect】
As described above, according to the present invention, by combining a membrane-separated activated sludge tank and a membrane-separated methane fermentation tank, the volume of excess sludge is reduced and the nitrogen component eluted with sludge decomposition during methane fermentation is removed. In the membrane separation methane fermentation tank, methane bacteria can be maintained at a high concentration, and the organic matter decomposition rate can be 40% or more in 1/2 to 1/3 of the conventional treatment time. The existing anaerobic wastewater treatment plant can be realized at a low cost for remodeling by employing the septic tank treatment method of the present invention, which is advantageous for local governments that are concerned with increasing septic tank sludge and aging urine treatment facilities.
[0027]
The use of a membrane separation activated sludge tank enables processing with a simple processing flow (see FIG. 2) and facilitates operation management. In addition, the activated sludge tank can be treated with a water tank capacity of 1/2 to 1/3 of the conventional one, and a compact treatment facility can be obtained.
[Brief description of the drawings]
FIG. 1 is a flow sheet diagram showing a method for treating septic tank sludge in an embodiment of the present invention.
FIG. 2 is a flow sheet diagram showing a method of treating septic tank sludge in another embodiment of the present invention.
FIG. 3 is a flow sheet diagram showing a method for treating septic tank sludge in another embodiment of the present invention.
FIG. 4 is a flow sheet diagram showing a conventional human waste treatment method.
FIG. 5 is a flow sheet diagram showing a conventional septic tank sludge treatment method.
[Explanation of symbols]
21 Septic tank sludge 22 Transport vehicle 23 Membrane separation activated sludge tank 24 Membrane separation methane fermentation tank

Claims

Septic tank sludge is subjected to biological denitrification in a membrane separation activated sludge tank, and the excess sludge is reduced in volume by methane fermentation in a membrane separation methane fermentation tank. A method for treating septic tank sludge, comprising performing biological denitrification.

Septic tank sludge is subjected to biological denitrification in a membrane separation activated sludge tank in a human waste treatment facility into which urine is transported as septic tank sludge, and is mixed with surplus sludge and urine in the membrane separation activated sludge tank to form a membrane separation methane fermentation tank. A method for treating septic tank sludge, comprising subjecting methane fermentation to activated sludge treatment of membrane permeated water of a membrane-separated methane fermentation tank.