JP3963497B2

JP3963497B2 - Organic wastewater treatment method and apparatus

Info

Publication number: JP3963497B2
Application number: JP11270596A
Authority: JP
Inventors: 晃延須山; 信二山本; 俊博田中
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 1996-05-07
Filing date: 1996-05-07
Publication date: 2007-08-22
Anticipated expiration: 2016-05-07
Also published as: JPH09294996A

Description

【０００１】
【発明の属する技術分野】
本発明は、事業場などから排出される有機性排水の活性汚泥処理方法において、汚泥と処理水の固液分離を活性汚泥処理槽に直接浸漬した膜により行う膜分離式活性汚泥法に関する。
【０００２】
【従来の技術】
図６に示すような従来の膜分離式活性汚泥方法を用いて有機性排水（以下、原水ともいう）１１の好気性処理を行う場合、活性汚泥を内蔵する活性汚泥処理槽１に分離膜（以下、単に膜ともいう）５のモジュールを直接浸透させ、吸引または水圧にて処理水１２を得るようにしているとともに、槽内の散気装置６を利用して分離膜５のろ過機能を維持する構造になっている。
有機性排水１１と活性汚泥の混合および反応、有機物の分解・除去、固液分離を活性汚泥処理槽１のみで行うことができるため、沈殿槽が不要となる。また、沈降分離の必要がなくなり、活性汚泥濃度を１０，０００ｍｇ／リットル程度の高い濃度で運転でき、活性汚泥処理槽１の容量を小さくすることができるため、設置スペースを削減できるという利点がある。また、固液分離に分離膜５を利用することによって、液中の固形分を確実に分離し、浮遊物を含まない良好な処理水１２を得ることができる。
【０００３】
【発明が解決しようとする課題】
しかし、処理を行う排水のＢＯＤ濃度が１，０００ｍｇ／リットルを越えると、分離膜５の汚染が著しく、膜５が目詰まりし、膜５を透過する水量の低下などが発生し、年に数回の洗浄が必要となった。このため、膜５の洗浄、水量の監視などの維持管理に手間がかかり、洗浄を繰り返すため、膜５の破損具合が増すことになってしまった。
【０００４】
発明者等は、実施設で検討した結果、膜近傍の残留ＢＯＤが高いと膜汚染が顕著になることが分かった。これは初めて明確に知られた膜汚染指標と言える。膜分離式活性汚泥法の場合、排水の流入から処理水の分離までを同一の槽で行い、反応槽容積が小さいため、排水の流入から膜を透過するまでの距離および時間が短くなる。排水の有機物濃度が高い場合、完全に混合・反応せずに充分に処理されないまま膜部を通過する恐れがあり、これにより処理水１２の水質が悪化したり膜５が汚染されることがある。生活排水、下水などの排水に適用していたときは流入ＢＯＤが１，０００ｍｇ／リットル以下と低く、原水１１が活性汚泥処理槽１内をショートパスにより、溶解性ＢＯＤが膜５を通過することで発生する膜汚染の影響が大きかった。
【０００５】
膜分離式活性汚泥方法において、膜５の目詰まりがなければ、維持管理を行う上で非常に容易な技術となる。従って、本発明は、膜分離式活性汚泥方法において、膜汚染を少なくすることで、膜５の洗浄頻度を少なくし、維持管理の手間をなくすとともに膜５の延命を図り、処理水量を確保するために、ろ過圧の上昇を抑える技術を提供することを課題とするものである。
【０００６】
【課題を解決するための手段】
本発明者は、鋭意検討の結果、排水の流入から膜を透過するまでの距離および時間を長くし、分離膜近傍での溶解性ＢＯＤが５〜１００ｍｇ／リットルであれば膜汚染は小さいことを見出し、この知見に基づいて本発明を成すに至った。
即ち、本発明は、
（１）膜分離式活性汚泥法による有機性排水の処理方法において、１以上の反応室を有し、少なくとも最初の反応室に有機性排水が導入され、最後の反応室からの流出水中の溶解性ＢＯＤが５〜１００ｍｇ／リットルとする反応工程と、前記反応工程から流出水を含酸素気体散気下で膜分離する分離工程と、分離工程における活性汚泥を含む分離残水を反応工程へ循環する循環工程とを有して成り、前記反応工程に微生物付着担体を投入し、反応工程と分離工程の間に該担体の回収手段を配備したことを特徴とする有機性排水の処理方法、
（２）前記反応工程において、有機性排水と循環工程からの分離残水とを混合した時のＢＯＤが５００〜７５０ｍｇ／リットルとなるようにすることを特徴とする前記（１）記載の有機性排水の処理方法、
【０００７】
（３）前記反応工程において、ＢＯＤ容積負荷が３．５〜６．０ｋｇ−ＢＯＤ／ｍ³ ・日、循環工程からの分離残水と有機性排水の混合水の滞留時間を２〜５時間とすることを特徴とする前記（１）記載の有機性排水の処理方法、上記処理を遂行する、
（４）活性汚泥処理槽中に浸漬分離膜を有する有機性排水の処理装置において、該活性汚泥処理槽が、最初の反応室に有機性排水が導入され、最後の反応室からの流出水中の溶解性ＢＯＤを５〜１００ｍｇ／リットルとする１以上の反応室と、槽内水ショートパス防止手段により離隔された分離膜を浸漬した分離室を有してなり、かつ該分離室から該反応室へ汚泥を循環する循環手段を有し、前記反応室に微生物付着担体が投入されており、前記反応室と分離室との間に該担体の回収手段を有することを特徴とする有機性排水の処理装置、である。
ここでいうショートパス防止手段としては、同一槽内におけるじゃま板、隔壁等を設けることの他、反応室と分離室を別々の槽としてこれらを連通した構成にしても良い。
【０００８】
【発明の実施の形態】
本発明の装置の例を、図１〜図４を示して以下に説明する。
本発明の装置は、活性汚泥処理槽１を別々の槽にするか、あるいは仕切２を入れて、１つ以上の反応室３と最後段の分離室４で構成されるものである。または、活性汚泥処理槽１内に邪魔板を設けることで、迂流させる構造とする。反応室３の流入・流出部は、槽１の上下あるいは左右と交互に設けるものとし、反応室３での流入・流出部の直線距離を長くとる。この条件とするには、これにより膜分離を行う分離室（工程）４での溶解性ＢＯＤを５〜１００ｍｇ／リットルとする。なお、図１は活性汚泥処理槽１を１つ反応室３と分離室４に仕切りした装置を、図２は活性汚泥処理槽１を２つの反応室３と分離室４に仕切りした装置の例を示し、図３は活性汚泥処理槽１を別々の槽にして２つの反応室３と分離室４とした装置の例を示す。
【０００９】
活性汚泥処理槽１全体での活性汚泥の容積負荷は、０．５〜５ｋｇ−ＢＯＤ／ｍ³ ・日以下となる槽容量とし、流入排水のＢＯＤが５００〜７５０ｍｇ／リットルに希釈されるだけの活性汚泥の混合液を最後段の分離室４から循環させる。１つの反応室３の容量は、ＢＯＤ容積負荷が３．５〜６．０ｋｇ−ＢＯＤ／ｍ³・日で循環水を含む滞留時間が２〜５時間になるものとし、分離室４を除いた反応槽４容積に対し、ａ個の反応室３を設ける。
【００１０】
室数ａは、以下の式で求める。
ａ＝Ｖ_R／Ｖ₁
ａ：反応室数〔室〕（整数：端数切り捨て）
ＶR ：反応室合計容量
Ｖ_R＝Ｖ_A−Ｖ_M
Ｖ_A：反応槽容量〔ｍ³〕
Ｖ_M：分離室容量〔ｍ³〕（分離膜を設置するための最小容量）
Ｖ₁：ＢＯＤ容積負荷が３．５〜６．０ｋｇ−ＢＯＤ／ｍ³・日、
循環水を含む滞留時間が２〜５時間となる。
反応室１室あたりの容積〔ｍ³〕
として室数を決定する。
【００１１】
前段の１つ以上の反応室３でＢＯＤを充分に吸着あるいは分解して溶解性ＢＯＤ濃度を５〜１００ｍｇ／リットルに除去した後、後段に設置した膜５によって吸引あるいは水圧で処理水１２を得る。また、後段に移流した活性汚泥は、循環水１３として最前段に移送し、再び原水１１と混合し反応させて処理するものとしたものである。
これにより、良好な水質の処理水１２を得るとともに、膜５の汚染の進行を緩慢にし、洗浄頻度を少なくし、同時に膜５の寿命を長くさせる。
本発明の要旨は膜汚染の指標をＳＳではなく膜近傍でのＢＯＤ、特に溶解ＢＯＤとすることが好ましいことを見出した点にあり、発明者の努力によりそのレベルを限定したものである。ＢＯＤ値は活性汚泥の作用で通常入口から除かれ減少するが、多くの膜汚染が高ＢＯＤ排水のショートパスによることがわかった。
【００１２】
活性汚泥処理槽１を複数の槽または槽内に仕切りを設けることで分割し、反応室３の最前段に原水１１の流入部を設け、最後段の分離室４に処理水１２を得るための膜５を設置する。各室には、酸素含有気体を曝気するための散気装置６を設け、必要に応じて各室の空気の量が調節できるようにする。個々の室および各室を通じて原水１１が充分に混合、反応できるように攪拌、迂流できる構造とする。また、最後段の分離室４に循環用ポンプ７を設置する。
原水（排水）１１は最前段の反応室３に流入させ、同時に槽内の液、好ましくは最後段分離室４の液を移流し、膜５の浸漬してない室３において混合・反応させる。膜５の浸漬した最後段の分離室４に移流したときには、残留する有機物濃度が溶解性ＢＯＤにして５〜１００ｍｇ／リットルとほとんどない状態となり膜５を通して吸引あるいは水圧で処理水１２を得る。膜５を透過する液に膜５の汚染源である有機物がほとんどないため、有機物による膜５の汚染の進行を極めて緩慢にすることができる。
【００１３】
さらに流入ＢＯＤ濃度が高い場合には、図４に示すように、膜５の浸漬しない反応室３においては、有機性ゲルからなる生物付着担体８を投入する。このとき、投入された反応室３により槽内液とともに担体８が後段の反応室３あるいは分離室４に移流してしまわないようにスクリーン９を設置する。反応室３に担体８を投入することで、反応室３における有機物の除去・分解を促進させ、分離室４での有機物の残留を少なくさせることができる。
【００１４】
【実施例】
以下、実施例にて本発明をさらに詳細に説明するが、本発明はこの実施例によって限定されるものではない。
〔実施例１〕
図５に示すように、活性汚泥処理槽１を前段１２ｍ³、中段１２．５ｍ³、後段１５．５ｍ³となるように槽内に仕切２を設けた。前段と中段の間の仕切２は、下側から移流できるように開口部を設け、中段と後段のあいだの仕切２は、上側を越流できるように開口部を設けてあるピストンフロー型となっている。膜５は、後段槽の最後部に浸漬設置しており、中空糸膜のモジュール（４ｍ／本）を２０本配置してある。後段の槽から前段に循環できるように循環ポンプ７を設置しており、流量調整槽１０から前段槽に排水が流入してくると、同時にこのポンプが作動し後段から前段へ活性汚泥の混合液を循環させ排水と混合させる。各段とも、散気装置６が設けられており、ＤＯが少なくとも１ｍｇ／リットル以上となるように散気させている。この槽を用いて、水量１５６ｍ³／日、ＢＯＤ４，０００ｍｇ／リットル、ＳＳ７００ｍｇ／リットルの排水を反応槽ＭＬＳＳ８，０００ｍｇ／リットルとして処理を行った。
【００１５】
排水は、いったん流量調整槽１０に貯留され、ここからなるべく定常的にポンプにて前段槽に移流される。処理水１２は、後段槽に浸漬した中空糸膜のモジュールに取り付けた配管の先にあるポンプにて吸引して得る。また、排水の流入と同時に循環ポンプを作動させ排水と循環水１３を混合したときのＢＯＤ濃度が５００〜７５０ｍｇ／リットルになって前段槽に移流されるように、循環水量を流入排水量の５倍程度になるように移流させた。
担体を入れずに上記の運転方法で、膜５の設置してある後段槽流入前のＢＯＤを９５ｍｇ／リットル以下で処理したところ、膜５は一年間汚染されずに、吸引圧力０．０５〜０．３ｋｇｆ／ｃｍ²で処理水１２が得られた。得られた処理水１２のＢＯＤは５ｍｇ／リットル以下であった。
【００１６】
〔実施例２〕
担体（粒径３〜５ｍｍ）を最前段の反応室３に１０％投入して、同一水質で水流２０ｍ³／日として処理した。循環水量を流入排水量の６倍程度になるように移流させて処理させたところ、膜５の設置してある後段流入前のＢＯＤを５０ｍｇ／リットル以下となり、同様に膜５は一年間汚染されずに、吸引圧力０．０５〜０．３０ｋｇｆ／ｃｍ²で処理水１２が得られ、処理水１２のＢＯＤは５ｍｇ／リットル以下であった。
【００１７】
〔比較例１〕
活性汚泥処理槽１内に仕切２を入れずに運転を行った場合、膜５のろ過圧は、約６か月経過した時点で、０．４ｋｇｆ／ｃｍ² を越え膜５の洗浄が必要になった。
比較例１に対して、槽１内に仕切２を入れた場合は、約１年経過した時点でも洗浄の必要がなく、０．３ｋｇｆ／ｃｍ² 以下であり、仕切２を入れピストンフロー型にすることで、膜５の汚染の進行を緩慢にし洗浄頻度を減らし、良好な処理水１２を得ることができた。
【００１８】
【発明の効果】
本発明は、活性汚泥処理槽を分割することによって、原水が活性汚泥処理槽に流入してから膜を透過するまでの経路が長く確保されており、ショートパスをする可能性がないため、有機物の分解（除去）の反応を十分に行うことができる。また、処理を完了した活性汚泥混合液を循環水として最前段の反応室で原水と混合させるために原水中の有機物と活性汚泥の接触・反応させる効率がよい。これらの作用により前段の反応室にて原水中の有機物を完全に除去してしまうことができ、後段の分離槽では、混合液中の溶解性ＢＯＤは１〜５ｍｇ／リットルとなる。このため、膜表面の生物の増殖をほぼ完全に抑制することができ、膜の有機物による汚染に起因する膜の目詰まりの発生がなくなった。この結果、膜を通過する透過水の水質が良好な状態で安定し、膜の洗浄頻度が少なくなり、膜の寿命も長くなった。
【図面の簡単な説明】
【図１】本発明の有機性汚水の処理装置の１例を示す図。
【図２】本発明の有機性汚水の処理装置の他の１例を示す図。
【図３】本発明の有機性汚水の処理装置の別の他の１例を示す図。
【図４】本発明の有機性汚水の処理装置の別の他の１例を示す図。
【図５】実施例に用いた有機性汚水の処理装置を示す図。
【図６】従来の有機性汚水の処理装置の１例を示す図。
【符号の説明】
１活性汚泥処理槽
２仕切
３反応槽
４分離槽
５分離膜
６散気装置
７循環用ポンプ
８担体
９スクリーン
１０流量調整槽
１１有機性排水
１２処理水
１３循環水[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an activated sludge treatment method for organic wastewater discharged from business establishments and the like, which relates to a membrane separation activated sludge method in which solid-liquid separation of sludge and treated water is performed by a membrane directly immersed in an activated sludge treatment tank.
[0002]
[Prior art]
When performing an aerobic treatment of organic wastewater (hereinafter also referred to as raw water) 11 using a conventional membrane separation type activated sludge method as shown in FIG. 6, a separation membrane (in the activated sludge treatment tank 1 containing the activated sludge ( In the following, the module 5 is directly permeated to obtain the treated water 12 by suction or water pressure, and the filtration function of the separation membrane 5 is maintained by using the diffuser 6 in the tank. It has a structure to do.
Since the mixing and reaction of the organic waste water 11 and the activated sludge, the decomposition / removal of the organic matter, and the solid-liquid separation can be performed only by the activated sludge treatment tank 1, no precipitation tank is required. In addition, there is no need for sedimentation separation, the activated sludge concentration can be operated at a high concentration of about 10,000 mg / liter, and the capacity of the activated sludge treatment tank 1 can be reduced, so that the installation space can be reduced. . Further, by using the separation membrane 5 for solid-liquid separation, it is possible to reliably separate the solid content in the liquid and to obtain a good treated water 12 that does not contain suspended solids.
[0003]
[Problems to be solved by the invention]
However, when the BOD concentration of the wastewater to be treated exceeds 1,000 mg / liter, the separation membrane 5 is significantly contaminated, the membrane 5 is clogged, and the amount of water passing through the membrane 5 is reduced. Washing was required. For this reason, the maintenance of the cleaning of the membrane 5 and the monitoring of the amount of water is time-consuming, and the cleaning is repeated, so that the degree of breakage of the membrane 5 is increased.
[0004]
As a result of investigations by the implementation facility, the inventors found that the membrane contamination becomes remarkable when the residual BOD near the membrane is high. This is the first clearly known membrane contamination index. In the case of the membrane-separated activated sludge method, the process from the inflow of drainage to the separation of treated water is performed in the same tank, and the reaction tank volume is small, so the distance and time from the inflow of drainage to permeate through the membrane are shortened. When the organic matter concentration of the wastewater is high, there is a risk of passing through the membrane part without being fully treated without being completely mixed and reacted, which may deteriorate the quality of the treated water 12 or contaminate the membrane 5. . When applied to wastewater such as domestic wastewater and sewage, the inflow BOD is as low as 1,000 mg / liter or less, and the raw water 11 passes through the activated sludge treatment tank 1 by a short path and the soluble BOD passes through the membrane 5. The effect of film contamination generated in
[0005]
In the membrane-separated activated sludge method, if the membrane 5 is not clogged, it becomes a very easy technique for maintenance. Therefore, in the membrane separation type activated sludge method, the present invention reduces the membrane contamination, thereby reducing the frequency of cleaning the membrane 5, eliminating the maintenance work, extending the life of the membrane 5, and securing the amount of treated water. Therefore, it is an object to provide a technique for suppressing an increase in filtration pressure.
[0006]
[Means for Solving the Problems]
As a result of intensive studies, the inventor has increased the distance and time from the inflow of drainage to permeate the membrane, and the membrane contamination is small if the solubility BOD in the vicinity of the separation membrane is 5 to 100 mg / liter. The present invention has been made based on the finding and this finding.
That is, the present invention
(1) In the processing method of the organic waste water by a membrane separation type activated sludge method, has one or more reaction chambers, organic waste water to at least the first reaction chamber is introduced, in the effluent from the last reaction chamber A reaction step in which the soluble BOD is 5 to 100 mg / liter, a separation step in which effluent water is separated from the reaction step under an oxygen-containing gas aeration, and separation separation water containing activated sludge in the separation step to the reaction step A method for treating organic wastewater, characterized in that a microorganism-adhering carrier is introduced into the reaction step, and a means for collecting the carrier is provided between the reaction step and the separation step.
(2) The organic property as described in (1) above, wherein, in the reaction step, the BOD is 500 to 750 mg / liter when the organic waste water and the separation residual water from the circulation step are mixed. Wastewater treatment method,
[0007]
(3) In the reaction step, the BOD volumetric load is 3.5 to 6.0 kg-BOD / m ³ · day, and the residence time of the mixed residual water from the circulation step and the organic waste water is 2 to 5 hours. wherein (1) of organic wastewater according how to process, characterized by, performing the upper SL process,
(4) In an organic wastewater treatment apparatus having an immersion separation membrane in an activated sludge treatment tank, the activated sludge treatment tank has an organic wastewater introduced into the first reaction chamber, and the effluent water from the last reaction chamber One or more reaction chambers having a soluble BOD of 5 to 100 mg / liter, and a separation chamber in which a separation membrane separated by water short path prevention means in the tank is immersed, and from the separation chamber to the reaction chamber The organic wastewater is characterized in that it has a circulation means for circulating sludge to the reaction chamber, a microorganism-adhering carrier is introduced into the reaction chamber, and a means for collecting the carrier is provided between the reaction chamber and the separation chamber. A processing device.
As a short path prevention means here, in addition to providing a baffle plate, a partition wall and the like in the same tank, the reaction chamber and the separation chamber may be separated and connected to each other.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An example of the apparatus of the present invention will be described below with reference to FIGS.
The apparatus of the present invention comprises an activated sludge treatment tank 1 as a separate tank or a partition 2 and is composed of one or more reaction chambers 3 and a separation chamber 4 at the last stage. Or it is set as the structure made to bypass by providing a baffle plate in the activated sludge processing tank 1. FIG. The inflow / outflow portions of the reaction chamber 3 are provided alternately with the upper and lower sides or the left and right sides of the tank 1, and the linear distance between the inflow / outflow portions in the reaction chamber 3 is increased. In order to satisfy this condition, the soluble BOD in the separation chamber (process) 4 for performing membrane separation is set to 5 to 100 mg / liter. 1 shows an apparatus in which one activated sludge treatment tank 1 is divided into a reaction chamber 3 and a separation chamber 4, and FIG. 2 shows an example of an apparatus in which the activated sludge treatment tank 1 is divided into two reaction chambers 3 and a separation chamber 4. FIG. 3 shows an example of an apparatus in which the activated sludge treatment tank 1 is made into separate tanks and has two reaction chambers 3 and a separation chamber 4.
[0009]
The volume load of activated sludge in the activated sludge treatment tank 1 as a whole is 0.5-5 kg-BOD / m ³ · day or less, and the BOD of the influent wastewater is only diluted to 500-750 mg / liter. The mixed liquid of activated sludge is circulated from the last separation chamber 4. The capacity of one reaction chamber 3 is such that the BOD volumetric load is 3.5 to 6.0 kg-BOD / m ³ · day, and the residence time including circulating water is 2 to 5 hours, and the separation chamber 4 is excluded. A number of reaction chambers 3 are provided for 4 volumes of the reaction tank.
[0010]
The number of rooms a is obtained by the following formula.
a = V _R / V ₁
a: Number of reaction chambers [room] (integer: rounded down)
VR: the reaction chamber the total capacity V _R = V _A -V _M
V _A : reaction tank capacity [m ³ ]
V _M : separation chamber capacity [m ³ ] (minimum capacity for installing a separation membrane)
V ₁ : BOD volumetric load is 3.5 to 6.0 kg-BOD / m ³ · day,
The residence time including circulating water is 2 to 5 hours.
Volume per reaction chamber [m ³ ]
Determine the number of rooms.
[0011]
After the BOD is sufficiently adsorbed or decomposed in one or more reaction chambers 3 in the previous stage to remove the soluble BOD concentration to 5 to 100 mg / liter, the treated water 12 is obtained by suction or water pressure with the membrane 5 installed in the subsequent stage. . Further, the activated sludge transferred to the latter stage is transferred to the foremost stage as the circulating water 13, and is mixed with the raw water 11 again to be treated.
As a result, the treated water 12 with good water quality is obtained, the progress of contamination of the membrane 5 is slowed, the frequency of cleaning is reduced, and at the same time the life of the membrane 5 is lengthened.
The gist of the present invention is that it has been found that it is preferable to set the index of film contamination to BOD in the vicinity of the film, not SS, particularly dissolved BOD, and the level is limited by the inventors' efforts. The BOD value is usually removed from the inlet by the action of activated sludge and decreases, but it has been found that many membrane contaminations are due to the short path of high BOD drainage.
[0012]
The activated sludge treatment tank 1 is divided by providing a plurality of tanks or partitions in the tank, an inflow portion of the raw water 11 is provided in the foremost stage of the reaction chamber 3, and the treated water 12 is obtained in the separation chamber 4 in the last stage. The membrane 5 is installed. Each chamber is provided with an air diffuser 6 for aeration of the oxygen-containing gas so that the amount of air in each chamber can be adjusted as necessary. The structure is such that the raw water 11 can be stirred and diverted so that the raw water 11 can be sufficiently mixed and reacted through each chamber and each chamber. A circulation pump 7 is installed in the separation chamber 4 at the last stage.
The raw water (drainage) 11 flows into the front reaction chamber 3, and at the same time, the liquid in the tank, preferably the liquid in the last separation chamber 4, is mixed and reacted in the chamber 3 where the membrane 5 is not immersed. When transferred to the separation chamber 4 at the last stage in which the membrane 5 is immersed, the concentration of the remaining organic substance becomes a soluble BOD of almost 5 to 100 mg / liter, and the treated water 12 is obtained through the membrane 5 by suction or water pressure. Since there is almost no organic matter that is a source of contamination of the membrane 5 in the liquid that permeates the membrane 5, the progress of contamination of the membrane 5 by the organic matter can be extremely slow.
[0013]
Further, when the inflow BOD concentration is high, as shown in FIG. 4, in the reaction chamber 3 where the membrane 5 is not immersed, the bioadhesive carrier 8 made of organic gel is introduced. At this time, the screen 9 is installed so that the carrier 8 together with the liquid in the tank is not transferred to the subsequent reaction chamber 3 or the separation chamber 4 by the charged reaction chamber 3. By introducing the carrier 8 into the reaction chamber 3, it is possible to promote the removal / decomposition of organic substances in the reaction chamber 3 and to reduce the residual of organic substances in the separation chamber 4.
[0014]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by this Example.
[Example 1]
As shown in FIG. 5, the partition 2 was provided in the tank so that the activated sludge treatment tank 1 had a front stage 12 m ³ , a middle stage 12.5 m ³ , and a rear stage 15.5 m ³ . The partition 2 between the front stage and the middle stage is provided with an opening so as to allow advection from the lower side, and the partition 2 between the middle stage and the rear stage is a piston flow type in which an opening is provided so that the upper part can overflow. ing. The membrane 5 is immersed in the rearmost part of the rear tank, and 20 hollow fiber membrane modules (4 m / piece) are arranged. A circulation pump 7 is installed so that it can circulate from the rear tank to the front stage. When the waste water flows into the front tank from the flow rate adjustment tank 10, this pump is activated at the same time and the mixed liquid of activated sludge from the rear stage to the front stage. Circulate and mix with waste water. Each stage is provided with an air diffuser 6 to diffuse air so that DO is at least 1 mg / liter. Using this tank, wastewater having a water volume of 156 m ³ / day, BOD of 4,000 mg / liter, and SS of 700 mg / liter was treated as a reaction tank MLSS of 8,000 mg / liter.
[0015]
The wastewater is once stored in the flow rate adjusting tank 10 and is transferred to the preceding tank by a pump as regularly as possible. The treated water 12 is obtained by suction with a pump at the end of a pipe attached to the module of the hollow fiber membrane immersed in the latter tank. In addition, when the circulation pump is operated simultaneously with the inflow of wastewater, the amount of circulating water is 5 times the amount of inflowing wastewater so that the BOD concentration becomes 500 to 750 mg / liter when the wastewater and the circulating water 13 are mixed and transferred to the preceding tank. The advection was carried out to the extent.
When the BOD before inflow of the latter tank where the membrane 5 was installed was treated at 95 mg / liter or less by the above operation method without putting the carrier, the membrane 5 was not contaminated for one year, and the suction pressure was 0.05 to Treated water 12 was obtained at 0.3 kgf / cm ² . The BOD of the obtained treated water 12 was 5 mg / liter or less.
[0016]
[Example 2]
10% of the support (particle size 3 to 5 mm) was put into the reaction chamber 3 at the foremost stage and treated with the same water quality as a water flow of 20 m ³ / day. When the amount of circulating water was transferred and treated to be about 6 times the amount of inflow wastewater, the BOD before the inflow of the latter stage where the membrane 5 was installed was 50 mg / liter or less, and similarly the membrane 5 was not contaminated for one year. Further, the treated water 12 was obtained at a suction pressure of 0.05 to 0.30 kgf / cm ² , and the BOD of the treated water 12 was 5 mg / liter or less.
[0017]
[Comparative Example 1]
When the operation is performed without putting the partition 2 in the activated sludge treatment tank 1, the filtration pressure of the membrane 5 exceeds 0.4 kgf / cm ² after about 6 months, and the membrane 5 needs to be cleaned. became.
The comparative example 1, when you put the partition 2 in the tank 1, there is no need for washing even after the lapse of about one year, and at 0.3 kgf / cm ² or less, the piston flow is entering the partition 2 By using a mold, the progress of contamination of the membrane 5 was slowed, the frequency of washing was reduced, and good treated water 12 could be obtained.
[0018]
【The invention's effect】
In the present invention, by dividing the activated sludge treatment tank, the path from the raw water flowing into the activated sludge treatment tank to the permeation of the membrane is ensured for a long time, and there is no possibility of making a short path. The decomposition (removal) reaction can be sufficiently performed. In addition, since the activated sludge mixed solution that has been treated is mixed with the raw water in the foremost reaction chamber as circulating water, the efficiency of contacting and reacting the organic matter in the raw water with the activated sludge is good. By these actions, organic substances in the raw water can be completely removed in the former reaction chamber, and the soluble BOD in the mixed solution is 1 to 5 mg / liter in the latter separation tank. For this reason, the growth of organisms on the surface of the membrane can be suppressed almost completely, and the occurrence of clogging of the membrane due to the contamination of the membrane with organic substances has been eliminated. As a result, the water quality of the permeated water passing through the membrane was stabilized in a good state, the frequency of membrane washing was reduced, and the membrane life was prolonged.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an organic wastewater treatment apparatus according to the present invention.
FIG. 2 is a view showing another example of the organic wastewater treatment apparatus of the present invention.
FIG. 3 is a view showing another example of the organic sewage treatment apparatus of the present invention.
FIG. 4 is a view showing another example of the organic sewage treatment apparatus of the present invention.
FIG. 5 is a view showing an organic sewage treatment apparatus used in Examples.
FIG. 6 is a diagram showing an example of a conventional organic wastewater treatment apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Activated sludge treatment tank 2 Partition 3 Reaction tank 4 Separation tank 5 Separation membrane 6 Air diffuser 7 Circulation pump 8 Carrier 9 Screen 10 Flow rate adjustment tank 11 Organic waste water 12 Treatment water 13 Circulation water

Claims

In the method of treating organic waste water by membrane separation type activated sludge method, has one or more reaction chambers, organic waste water to at least the first reaction chamber is introduced, the solubility BOD in the effluent from the last reaction chamber Is a reaction step of 5 to 100 mg / liter, a separation step of separating the effluent water from the reaction step under an oxygen-containing gas diffusion, and a circulation for circulating the separated residual water containing activated sludge in the separation step to the reaction step An organic wastewater treatment method, wherein a microorganism-adhering carrier is introduced into the reaction step, and a means for collecting the carrier is provided between the reaction step and the separation step.

2. The method for treating organic wastewater according to claim 1, wherein the BOD is 500 to 750 mg / liter when the organic wastewater and the separation residual water from the circulation step are mixed in the reaction step. .

In the reaction step, the BOD volumetric load is 3.5 to 6.0 kg-BOD / m ³ · day, and the residence time of the mixed water of the separation residual water and the organic waste water from the circulation step is 2 to 5 hours. The organic wastewater treatment method according to claim 1, wherein the organic wastewater is treated .

In the processing apparatus of organic waste water with immersion separation membrane bioreactor tank in said active sludge treatment tank, organic waste water in the first reaction chamber is introduced, the solubility of the water flowing out from the end of the reaction chamber One or more reaction chambers having a BOD of 5 to 100 mg / liter, and a separation chamber in which a separation membrane separated by water short path prevention means in the tank is immersed, and sludge from the separation chamber to the reaction chamber A circulatory means for circulating the water, and further, a microorganism-adhering carrier is introduced into the reaction chamber, and a means for collecting the carrier is provided between the reaction chamber and the separation chamber. Processing equipment.