JP3870481B2 - Wastewater treatment equipment - Google Patents

Wastewater treatment equipment Download PDF

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JP3870481B2
JP3870481B2 JP11812297A JP11812297A JP3870481B2 JP 3870481 B2 JP3870481 B2 JP 3870481B2 JP 11812297 A JP11812297 A JP 11812297A JP 11812297 A JP11812297 A JP 11812297A JP 3870481 B2 JP3870481 B2 JP 3870481B2
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tank
liquid
biological treatment
separation
membrane
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JPH10309594A (en
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和夫 鈴木
謙介 松井
邦博 岩崎
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Kurita Water Industries Ltd
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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
    • 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

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Description

【０００１】
【発明の属する技術分野】
本発明は、排水を生物処理する生物処理手段と、この生物処理液を膜分離する膜分離手段とを有した排水処理装置に関する。
【０００２】
【従来の技術】
窒素及びリンを含む有機性排水の処理装置として、生物処理手段と膜分離手段とを備えたものがある。
【０００３】
図２はこの排水処理装置の従来例を示す系統図である。この排水処理装置の生物処理槽においては、硝化処理水循環管２４によって硝化処理水を循環返送し、凝集処理液返送管２５によって凝集処理液を返送する。原水供給管２２より窒素やリンを含む原水を嫌気槽１７に供給すると、原水は槽内において、脱窒菌を主とする微生物からなる活性汚泥、硝化処理水、および凝集処理液と、撹拌装置２３により撹拌混合される。この混合液中に含まれる硝酸性窒素や亜硝酸性窒素が嫌気条件下に脱窒菌の硝酸呼吸によって窒素ガスまで還元されるとともに生物分解性有機物が分解され、槽内で脱窒された脱窒処理水が好気槽１８に流出する。
【０００４】
好気槽１８に流入した脱窒処理水は、ブロワー３１より散気装置３２を通じて空気が供給される好気的条件下で、槽内の硝化菌を主体とする微生物からなる活性汚泥と混合され、この混合液中に含まれる有機性窒素やアンモニア性窒素は硝化菌の酸化作用によって亜硝酸性窒素や硝酸性窒素に硝化される。槽内で硝化された硝化処理水は、循環ポンプ２６により硝化処理水返送管２４を通って嫌気槽１７へ返送され、再び脱窒作用を受ける。好気槽１８内に滞留してくる余剰汚泥は汚泥引抜管２７によって引き抜く。
【０００５】
吸引ポンプ２９により膜透過水取出管３０を通じて浸漬型膜分離装置２８に吸引負圧を作用させると、槽内の硝化処理水は膜分離装置２８により固液分離されて、窒素分は除去されているがリンをリン酸イオンの形態で含む膜透過水が膜透過水取出管３０へと取り出される。膜透過水取出管３０へ取り出された膜透過水は、ＲＯ（逆浸透）膜保護用のカートリッジフィルター３３を通って、打込ポンプ３４によってＲＯ膜濾過装置１９に圧送される。ＲＯ膜を透過した脱塩水が脱塩水取出管３５によって取り出される。一方、リン酸イオンやその他のイオン類並びに有機物を含む濃縮液が濃縮液返送管３６によって凝集混和槽２０へ送られる。そして、槽２０内で凝集剤供給管３７より供給される硫酸バンド、ポリ塩化アルミニウム、塩化第２鉄、ポリ硫酸第２鉄などの凝集剤と混和され、濃縮液中のリン酸イオンやその他のイオン類や有機物が凝集される。この凝集物を含む凝集処理液は沈降槽２１へ送られ、リンや有機物を含む沈降凝集物が凝集物引抜管３８によって適宜引き抜かれるとともに、上澄液は凝集処理液返送管２５によって嫌気槽１７へ返送される。
【０００６】
【発明が解決しようとする課題】
生物処理手段と膜分離手段とを組み合わせた上記図２の排水処理装置においては、次の▲１▼、▲２▼のような短所があった。
▲１▼ 生物処理槽内に浸漬型分離膜を設置する場合、膜面の汚れを防止することと、動力（吸引ポンプ消費電力）の低減を図ることが重要である。そして、これらのためには、浸漬型分離膜の透過水量を少なくすることが必要となる。
ところが、上記図２の排水処理装置においては、ＲＯ膜濾過装置１９の濃縮水に凝集剤を添加した後、固液分離（沈降分離）し、この固液分離により得られた水（上澄水）をすべて生物処理装置１７、１８へ戻すようにしているところから嫌気槽１７への返送水量が多くなり、浸漬型膜分離装置２８の透過水量（フラックス）を著しく多くしなければならない。この結果、浸漬型膜分離装置２８の透過膜の膜面に汚れ（ゲル層）が堆積し易いと共に、ポンプ２９の消費動力も大きい。
▲２▼ ＲＯ膜濾過装置１９は目詰りし易く、安定運転が難しい。
【０００７】
本発明は、このような問題点を解決し、浸漬型膜分離手段の膜面の汚れ（ゲル層生成）が少なく、ポンプ動力コストが低く、安定運転が可能な排水処理装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明の排水処理装置は、生物処理槽と、該生物処理槽とは別体であり、該生物処理槽から生物処理液を受け入れると共に、この生物処理液を固液分離処理する第１の浸漬型膜分離手段を備えた固液分離槽と、該固液分離槽とは別体であり、該浸漬型膜分離手段からの透過水を受け入れると共に、該透過水に凝集剤を添加する凝集槽と、該凝集槽とは別体であり、該凝集槽からの凝集剤が添加された液を受け入れると共に、この液を固液分離処理する第２の浸漬型膜分離手段を備えた凝集分離槽と、該生物処理槽又は該固液分離槽から余剰汚泥が導入され、この余剰汚泥を脱水し、脱水濾液を前記生物処理槽へ送る汚泥脱水機と、からなり、該第２の浸漬型膜分離手段の透過水を処理水として取り出し、濃縮液は該凝集分離槽から前記生物処理槽へ返送するようにしたことを特徴とするものである。
【０００９】
かかる排水処理装置においては、生物処理槽で処理された生物処理液が固液分離槽に導入され、第１の浸漬型膜分離手段で膜分離される。
【００１０】
この透過液に凝集槽で凝集剤が添加され、次いで凝集分離槽にて第２の浸漬型膜分離手段で膜分離処理される。この透過水が処理水として取り出される。凝集汚泥を含む液は、この第２の浸漬型膜分離手段を有した凝集分離槽から生物処理槽へ返送される。第２の浸漬型膜分離手段においては凝集剤が添加された液を膜分離するため、透過水量を多くすることができ、該凝集分離槽から生物処理手段へ返送される返送液量を著しく少なくすることができる。この結果、固液分離槽内に設けられた第１の浸漬型膜分離手段の透過水量を少なく押えることができ、その膜面への汚れの堆積を減少できると共に、ポンプ動力も少なくて済む。
【００１１】
なお、第２の浸漬型膜分離手段は、ＲＯ膜濾過装置に比べ目詰りしにくく、運転が安定している。
【００１２】
【発明の実施の形態】
図１は実施の形態に係る排水処理装置の系統図である。
【００１３】
原水配管１から導入された有機性排水は、生物処理槽２においてブロワー３からの空気が散気管２ａによって吹き込まれることにより好気的に生物処理され、固液分離槽４に移送される。生物処理水は、この槽４内において、第１の浸漬型膜分離手段としての分離膜５により固液分離される。該分離膜５によって濃縮された液は、返送管１４によって返送汚泥として生物処理槽２へ返送される。
【００１４】
分離膜５の透過水は吸引ポンプ６を経て凝集槽８内に導入され、撹拌機８ａで撹拌されつつ凝集剤及び必要ならばさらに中和剤が添加手段７により添加される。これによりリンや高分子有機物などが不溶化される。この薬剤が添加された液は、凝集分離槽９に導入され、第２の浸漬型膜分離手段としての分離膜１０により固液分離され、透過水は処理水として吸引ポンプ１１を経て取り出される。凝集分離槽９で濃縮された液は、配管１５により凝集汚泥として生物処理槽２へ返送される。生物処理槽２で生成した余剰汚泥は、生物処理槽２から配管１２により、又は固液分離槽４から配管１３により適宜引抜かれ、脱水機１６により脱水処理される。脱水ケーキは系外へ排出され、脱水濾液は配管１６ａによって生物処理槽２へ送られる。
【００１５】
なお、固液分離槽４では、分離膜５の下方に散気管５ａを配置し、凝集分離槽９においては、分離膜１０の下方に散気管９ａを配置している。これらの散気管５ａ，９ａにもブロワー３から空気が供給される。
【００１６】
この排水処理装置においては、第１の浸漬型膜分離手段としての分離膜５を透過した液に凝集剤が添加され、この凝集液が凝集分離槽９内において第２の浸漬型膜分離手段たる分離膜１０によって固液分離される。この分離膜１０は、従って（未凝集状態の液を透過処理する場合に比べ）膜面へのケーキ層堆積が少なく、低動力にて多くの透過水を得ることができる。この結果、配管１５から生物処理槽２へ返送される濃縮液量が少ないものとなり、第１の浸漬型膜分離手段たる分離膜５の透過水量を少なく押えることができ、該分離膜５の膜面閉塞を抑制できる。加えて、吸引ポンプ６の消費動力も少なくて済む。
【００１７】
なお、この図１の排水処理装置のその他の作用について次に説明する。
【００１８】
▲１▼ 生物処理槽２内での汚泥のＳＲＴ（汚泥滞留時間）は、短いもので１０日程度以上、し尿処理のように硝化脱窒処理する場合には１ケ月以上のものもあり、汚泥の濃度等の性状は比較的安定している。これに対して配管１５から引き抜かれる凝集汚泥の場合のＳＲＴは、数日以下が一般的であり、引き抜かれる汚泥の性状は変動し易い。また、凝集槽８では、分離膜５の透過水に凝集剤を添加しているため、槽８，９における凝集汚泥の生成量も通常の生物処理での余剰汚泥に比較してはるかに少ない。これらのことから、凝集汚泥を生物処理槽２に流入させ、余剰汚泥として引き抜くことにより、均質な脱水原泥が得られるという効果が奏される。
凝集槽８に添加する凝集剤としては、塩化第２鉄やポリ硫酸鉄などの鉄塩や硫酸バンド、ＰＡＣなどのアルミニウム塩が用いられる。これらにより生成した凝集汚泥は生物処理の機能に何ら障害を与えず、むしろ、生物処理で活性汚泥が腐敗した場合に発生するＨ2 ＳをＦｅＳやＦｅ2 Ｓ3 として不溶化し、その毒性を解消することができる。
【００１９】
▲２▼ ところで、一般に浸漬吸引型の分離膜においては、その分離膜モジュールの下部より散気し、それによる液流速により膜面でのケーキ層やゲル層の付着を防止している。しかし、散気による液流速は通常、膜面流速０．５〜１．０ｍ／ｓ程度と小さい値である。（ちなみに、ＵＦ膜分離では、１．５〜２．５ｍ／ｓである。）そして、前記のような曝気による液流速下では、ＳＳ濃度が高くなると膜面でのケーキ層、ゲル層の形成が激しくなり、安定した膜分離性能が得られなくなる。この傾向は凝集処理の場合、一層顕著に現われる。
本発明では凝集汚泥を生物処理槽に流入させることにより固液分離槽４の汚泥濃度管理が行えるようになるので安定した分離膜性能を得やすくなる。
なお、凝集汚泥を生物処理槽２へ投入することで生物処理槽２、固液分離槽４での汚泥濃度が多少増加する。しかし、前述のように凝集汚泥の生成量は、生物処理槽２の容量および余剰汚泥量に比較して少ないので、これによる生物処理槽２、固液分離槽４での汚泥濃度の増加は少ない。更に、凝集汚泥の粘性は、生物処理での活性汚泥ほど高くないため、これを添加しても曝気による液流に与える影響は少ない。
【００２０】
▲３▼ 一般に、生物処理水中には、有機物等が生分解される際に発生する重炭酸イオン（ＨＣＯ3 -）が含まれる。特に脱窒処理を行った場合には、除去ＮＯｘ−Ｎ１ｋｇ当りＣａＣＯ3 として約７ｋｇも生成する。これが、凝集工程に流入するとこのＨＣＯ3 -と凝集剤が中和反応し、凝集剤が水酸化物となり、除去すべきリンや高分子有機物が十分には除去されず余分な凝集剤が必要となる。
従来技術では、凝集汚泥は、そのまま脱水処理されてしまうが、本発明においては、凝集汚泥を生物処理槽２へ流入させることにより、水酸化物となった凝集剤を有効利用することができる。
生物処理槽２は、前述のように一般に長いＳＲＴで運転されるため、流入した凝集汚泥中の未利用の水酸化物凝集剤は排水中のリンや難生分解性高分子有機物と化合し、これらを不溶化させる。これにより、生物処理水中のリン等の濃度が低下し、従来のものに比較して、良好な処理水質が得られる。
【００２１】
【発明の効果】
以上の通り、本発明の排水処理装置は、浸漬型膜分離手段の膜面の汚れが少なくて、長期にわたって安定運転可能である。また、膜分離処理のためのポンプの消費動力が少なく、処理動力コストも低廉となる。
【図面の簡単な説明】
【図１】実施の形態に係る排水処理装置の系統図である。
【図２】従来例に係る排水処理装置の系統図である。
【符号の説明】
２ 生物処理槽
４ 固液分離槽
５ 分離膜
８ 凝集槽
９ 凝集分離槽
１０ 分離膜
１６ 脱水機[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment apparatus having biological treatment means for biologically treating wastewater and membrane separation means for membrane-separating this biological treatment liquid.
[0002]
[Prior art]
As an apparatus for treating organic wastewater containing nitrogen and phosphorus, there is one provided with a biological treatment means and a membrane separation means.
[0003]
FIG. 2 is a system diagram showing a conventional example of this waste water treatment apparatus. In the biological treatment tank of this waste water treatment apparatus, the nitrification water is circulated and returned by the nitrification water circulation pipe 24, and the aggregation treatment liquid is returned by the aggregation treatment liquid return pipe 25. When raw water containing nitrogen or phosphorus is supplied from the raw water supply pipe 22 to the anaerobic tank 17, the raw water is activated sludge composed of microorganisms mainly composed of denitrifying bacteria, nitrification water, aggregating liquid, and a stirring device 23. Is mixed with stirring. Nitrate nitrogen and nitrite nitrogen contained in this mixture are reduced to nitrogen gas by nitric acid respiration of denitrifying bacteria under anaerobic conditions, and biodegradable organic substances are decomposed and denitrified in the tank. The treated water flows out to the aerobic tank 18.
[0004]
The denitrification water that has flowed into the aerobic tank 18 is mixed with activated sludge composed of microorganisms mainly composed of nitrifying bacteria in the tank under aerobic conditions in which air is supplied from the blower 31 through the diffuser 32. Organic nitrogen and ammonia nitrogen contained in this mixed solution are nitrified to nitrite nitrogen and nitrate nitrogen by the oxidizing action of nitrifying bacteria. The nitrification water nitrified in the tank is returned to the anaerobic tank 17 through the nitrification water return pipe 24 by the circulation pump 26, and again receives a denitrification action. Excess sludge staying in the aerobic tank 18 is extracted by a sludge extraction tube 27.
[0005]
When a suction negative pressure is applied to the submerged membrane separation device 28 through the membrane permeate take-out pipe 30 by the suction pump 29, the nitrification water in the tank is solid-liquid separated by the membrane separation device 28, and the nitrogen content is removed. However, the permeated water containing phosphorus in the form of phosphate ions is taken out to the permeated water outlet pipe 30. The membrane permeated water taken out to the membrane permeated water extraction pipe 30 passes through the cartridge filter 33 for protecting the RO (reverse osmosis) membrane and is pumped to the RO membrane filtration device 19 by the driving pump 34. Demineralized water that has permeated through the RO membrane is taken out by a demineralized water extraction pipe 35. On the other hand, a concentrate containing phosphate ions, other ions, and organic substances is sent to the agglomeration mixing tank 20 through the concentrate return pipe 36. Then, it is mixed with a coagulant such as sulfuric acid band, polyaluminum chloride, ferric chloride, polyferric sulphate, etc., supplied from the coagulant supply pipe 37 in the tank 20, and phosphate ions in the concentrate or other Ions and organic substances are aggregated. The coagulation treatment liquid containing the aggregate is sent to the sedimentation tank 21, and the sedimentation aggregate containing phosphorus and organic matter is appropriately extracted by the aggregate extraction pipe 38, and the supernatant is anaerobic tank 17 by the aggregation treatment liquid return pipe 25. Will be returned to.
[0006]
[Problems to be solved by the invention]
The waste water treatment apparatus of FIG. 2 combined with the biological treatment means and the membrane separation means has the following disadvantages (1) and (2).
(1) When an immersion type separation membrane is installed in a biological treatment tank, it is important to prevent contamination of the membrane surface and reduce power (suction pump power consumption). For these reasons, it is necessary to reduce the amount of permeated water of the immersion type separation membrane.
However, in the waste water treatment apparatus of FIG. 2 described above, after adding a flocculant to the concentrated water of the RO membrane filtration apparatus 19, solid-liquid separation (sedimentation separation) is performed, and water obtained by this solid-liquid separation (supernatant water). Since all the water is returned to the biological treatment devices 17 and 18, the amount of water returned to the anaerobic tank 17 is increased, and the amount of permeated water (flux) of the submerged membrane separation device 28 must be remarkably increased. As a result, dirt (gel layer) is easily deposited on the membrane surface of the permeable membrane of the submerged membrane separation device 28, and the power consumption of the pump 29 is large.
(2) The RO membrane filtration device 19 is easily clogged and difficult to operate stably.
[0007]
The present invention solves such problems, and provides a wastewater treatment apparatus capable of stable operation with less contamination (gel layer generation) on the membrane surface of the submerged membrane separation means, low pump power cost, and the like. Objective.
[0008]
[Means for Solving the Problems]
The waste water treatment apparatus of the present invention is separate from the biological treatment tank and the biological treatment tank, and receives a biological treatment liquid from the biological treatment tank, and also performs a first liquid immersion treatment for solid-liquid separation of the biological treatment liquid. The solid-liquid separation tank provided with the mold membrane separation means and the solid-liquid separation tank are separate from each other and receive the permeated water from the immersion type membrane separation means and add a flocculant to the permeated water And a coagulation separation tank provided with a second submerged membrane separation means for receiving the liquid to which the coagulant is added from the coagulation tank and performing a solid-liquid separation process on the liquid. And a sludge dehydrator that introduces excess sludge from the biological treatment tank or the solid-liquid separation tank, dehydrates the excess sludge, and sends the dehydrated filtrate to the biological treatment tank, and the second submerged membrane removed permeate of the separating means as treated water, concentrate the biological treatment from agglomerated separation tank It is characterized in that it has to be returned to the tank.
[0009]
In such wastewater treatment system, biological treatment liquid treated in the biological treatment tank is introduced into the solid-liquid separation tank are membrane separation in the first submerged membrane separation unit.
[0010]
A flocculant is added to this permeate in a flocculation tank, and then a membrane separation treatment is performed in the flocculation tank by a second submerged membrane separation means. This permeated water is taken out as treated water. The liquid containing the coagulated sludge is returned to the biological treatment tank from the coagulation separation tank having the second submerged membrane separation means. To membrane separating the liquid coagulant is added in the second submerged membrane separation unit, it is possible to increase the amount of permeated water, significantly reducing the liquid-return amount sent back from the flocculation separation tank to the biological treatment means can do. As a result, the amount of permeated water of the first submerged membrane separation means provided in the solid-liquid separation tank can be suppressed, the accumulation of dirt on the membrane surface can be reduced, and the pump power can be reduced.
[0011]
The second submerged membrane separation means is less clogged than the RO membrane filtration device, and the operation is stable.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a system diagram of a wastewater treatment apparatus according to an embodiment.
[0013]
The organic wastewater introduced from the raw water pipe 1 is aerobically biologically treated by blowing air from the blower 3 through the diffuser pipe 2 a in the biological treatment tank 2 and transferred to the solid-liquid separation tank 4. The biologically treated water is solid-liquid separated in the tank 4 by a separation membrane 5 as a first submerged membrane separation means. The liquid concentrated by the separation membrane 5 is returned to the biological treatment tank 2 as return sludge by the return pipe 14.
[0014]
The permeated water of the separation membrane 5 is introduced into the coagulation tank 8 through the suction pump 6, and the coagulant and, if necessary, the neutralizing agent are further added by the adding means 7 while being stirred by the agitator 8 a. This insolubilizes phosphorus, polymer organic matter, and the like. The liquid to which this chemical is added is introduced into the agglomeration / separation tank 9 and separated into solid and liquid by the separation membrane 10 as the second submerged membrane separation means, and the permeated water is taken out through the suction pump 11 as treated water. The liquid concentrated in the coagulation / separation tank 9 is returned to the biological treatment tank 2 as coagulated sludge through the pipe 15. Excess sludge generated in the biological treatment tank 2 is appropriately extracted from the biological treatment tank 2 through the pipe 12 or from the solid-liquid separation tank 4 through the pipe 13 and dehydrated by the dehydrator 16. The dehydrated cake is discharged out of the system, and the dehydrated filtrate is sent to the biological treatment tank 2 through the pipe 16a.
[0015]
In the solid-liquid separation tank 4, an air diffuser 5 a is disposed below the separation membrane 5, and in the coagulation separation tank 9, an air diffuser 9 a is disposed below the separation membrane 10. Air is also supplied from the blower 3 to these air diffusers 5a and 9a.
[0016]
In this waste water treatment apparatus, a flocculant is added to the liquid that has permeated through the separation membrane 5 as the first submerged membrane separation means, and this agglomerated liquid serves as the second submerged membrane separation means in the agglomeration separation tank 9. Solid-liquid separation is performed by the separation membrane 10. Therefore, the separation membrane 10 has less cake layer deposition on the membrane surface (compared with the case where the non-aggregated liquid is permeabilized) and can obtain a large amount of permeated water with low power. As a result, the amount of the concentrated liquid returned from the pipe 15 to the biological treatment tank 2 becomes small, and the amount of permeated water of the separation membrane 5 serving as the first submerged membrane separation means can be suppressed. Surface blockage can be suppressed. In addition, the power consumption of the suction pump 6 can be reduced.
[0017]
The other operation of the waste water treatment apparatus of FIG. 1 will be described next.
[0018]
(1) SRT (sludge retention time) of the sludge in the biological treatment tank 2 is short, about 10 days or more, and in the case of nitrification / denitrification treatment such as human waste treatment, there are also one month or more. The properties such as concentration are relatively stable. On the other hand, the SRT in the case of the coagulated sludge drawn out from the pipe 15 is generally several days or less, and the properties of the sludge drawn out are likely to fluctuate. Moreover, in the coagulation tank 8, since the coagulant is added to the permeated water of the separation membrane 5, the amount of coagulated sludge produced in the tanks 8 and 9 is much smaller than the excess sludge in normal biological treatment. From these things, the effect | action that homogeneous dehydrated raw mud is obtained by making the coagulated sludge flow into the biological treatment tank 2 and extracting it as surplus sludge.
As the aggregating agent to be added to the aggregating tank 8, an iron salt such as ferric chloride or polyiron sulfate, or an aluminum salt such as sulfuric acid band or PAC is used. The aggregated sludge produced by these methods does not impair the function of biological treatment. Rather, H 2 S generated when activated sludge decays in biological treatment is insolubilized as FeS or Fe 2 S 3 , eliminating its toxicity. can do.
[0019]
(2) By the way, in the submerged suction type separation membrane, generally, air diffuses from the lower part of the separation membrane module, and the liquid flow rate thereby prevents the cake layer and the gel layer from adhering to the membrane surface. However, the liquid flow rate due to aeration is usually a small value of about 0.5 to 1.0 m / s. (By the way, in UF membrane separation, it is 1.5 to 2.5 m / s.) And, under the liquid flow rate by aeration as described above, when the SS concentration becomes high, formation of a cake layer and a gel layer on the membrane surface Becomes unstable and stable membrane separation performance cannot be obtained. This tendency appears more prominently in the case of the aggregation treatment.
In the present invention, since the sludge concentration in the solid-liquid separation tank 4 can be controlled by allowing the agglomerated sludge to flow into the biological treatment tank, it becomes easy to obtain stable separation membrane performance.
In addition, the sludge density | concentration in the biological treatment tank 2 and the solid-liquid separation tank 4 increases a little by throwing agglomerated sludge into the biological treatment tank 2. FIG. However, as described above, the amount of coagulated sludge produced is small compared to the capacity of the biological treatment tank 2 and the amount of excess sludge, so that the increase in the sludge concentration in the biological treatment tank 2 and the solid-liquid separation tank 4 is small. . Furthermore, since the viscosity of the coagulated sludge is not as high as that of activated sludge in biological treatment, the addition of this has little effect on the liquid flow due to aeration.
[0020]
(3) In general, biologically treated water contains bicarbonate ions (HCO 3 − ) that are generated when organic substances are biodegraded. In particular, when denitrification is performed, about 7 kg of CaCO 3 is generated per 1 kg of removed NOx—N. When this flows into the agglomeration process, the HCO 3 − and the aggregating agent are neutralized, the aggregating agent becomes a hydroxide, and the phosphorus and polymer organic matter to be removed are not sufficiently removed, and an extra aggregating agent is required. Become.
In the prior art, the coagulated sludge is dehydrated as it is, but in the present invention, the coagulant that has become hydroxide can be effectively used by flowing the coagulated sludge into the biological treatment tank 2.
Since the biological treatment tank 2 is generally operated with a long SRT as described above, the unused hydroxide flocculant in the infused sludge is combined with phosphorus in the wastewater and the hardly biodegradable polymer organic matter, These are insolubilized. Thereby, the density | concentrations, such as phosphorus in biologically treated water, fall and a favorable treated water quality is obtained compared with a conventional thing.
[0021]
【The invention's effect】
As described above, the waste water treatment apparatus of the present invention is less likely to contaminate the membrane surface of the submerged membrane separation means and can be stably operated over a long period of time. Further, the power consumption of the pump for the membrane separation process is small, and the processing power cost is low.
[Brief description of the drawings]
FIG. 1 is a system diagram of a wastewater treatment apparatus according to an embodiment.
FIG. 2 is a system diagram of a wastewater treatment apparatus according to a conventional example.
[Explanation of symbols]
2 biological treatment tank 4 solid-liquid separation tank 5 separation membrane 8 coagulation tank 9 coagulation separation tank 10 separation membrane 16 dehydrator

Claims (1)

生物処理槽と、
該生物処理槽とは別体であり、該生物処理槽から生物処理液を受け入れると共に、この生物処理液を固液分離処理する第１の浸漬型膜分離手段を備えた固液分離槽と、
該固液分離槽とは別体であり、該浸漬型膜分離手段からの透過水を受け入れると共に、該透過水に凝集剤を添加する凝集槽と、
該凝集槽とは別体であり、該凝集槽からの凝集剤が添加された液を受け入れると共に、この液を固液分離処理する第２の浸漬型膜分離手段を備えた凝集分離槽と、
該生物処理槽又は該固液分離槽から余剰汚泥が導入され、この余剰汚泥を脱水し、脱水濾液を前記生物処理槽へ送る汚泥脱水機と、からなり、
該第２の浸漬型膜分離手段の透過水を処理水として取り出し、濃縮液は該凝集分離槽から前記生物処理槽へ返送するようにしたことを特徴とする排水処理装置。A biological treatment tank;
A solid-liquid separation tank that is separate from the biological treatment tank and that includes a first treatment type membrane separation unit that receives a biological treatment liquid from the biological treatment tank and performs a solid-liquid separation process on the biological treatment liquid;
A coagulation tank that is separate from the solid-liquid separation tank, receives permeate from the submerged membrane separation means, and adds a coagulant to the permeate;
A flocculent separation tank provided with a second submerged membrane separation means for receiving a liquid to which a flocculant is added from the flocculant and receiving the liquid added from the flocculant and performing a solid-liquid separation process on the liquid;
Surplus sludge is introduced from the biological treatment tank or the solid-liquid separation tank, and the excess sludge is dehydrated, and a sludge dehydrator that sends the dehydrated filtrate to the biological treatment tank,
A wastewater treatment apparatus, wherein the permeated water of the second submerged membrane separation means is taken out as treated water, and the concentrated liquid is returned from the coagulation separation tank to the biological treatment tank.
JP11812297A 1997-05-08 1997-05-08 Wastewater treatment equipment Expired - Fee Related JP3870481B2 (en)

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