JP3707293B2

JP3707293B2 - Wastewater treatment equipment

Info

Publication number: JP3707293B2
Application number: JP11111199A
Authority: JP
Inventors: 繁樹澤田
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 1999-04-19
Filing date: 1999-04-19
Publication date: 2005-10-19
Anticipated expiration: 2019-04-19
Also published as: JP2000301174A

Description

【０００１】
【発明の属する技術分野】
本発明は、原水をオゾン酸化処理し、オゾン処理水を膜分離処理する用排水処理装置に関する。
【０００２】
【従来の技術及び先行技術】
従来、用水ないし排水処理における逆浸透（ＲＯ）膜分離装置等の浄化設備の前処理システムとしては、一般的に、凝集・沈殿・砂濾過からなるシステムが採用されていたが、この前処理システムでは、原水の有機物濃度が高まると、塩化第二鉄、ポリ塩化アルミニウム、硫酸アルミニウム等の凝集剤を多量に添加する必要があるという欠点がある。また、原水の水質変動に対応した凝集剤添加量の調整が必要であり、適正な添加量制御が行われない場合には、処理水の水質が悪化するという問題もあった。
【０００３】
このため、このような旧来の前処理プロセスに替わって、精密濾過（ＭＦ）膜や限外濾過（ＵＦ）膜等を用いた膜分離処理が採用されるようになってきている。ＭＦ膜やＵＦ膜によれば、凝集剤を添加することなく、又は微量の凝集剤の添加だけで、後段のＲＯ膜を汚染させるコロイド状成分を除去することができ、ＲＯ膜の汚染を抑止してその薬品洗浄間隔を延ばし、ＲＯ膜分離装置の運転を効率化させることができる。
【０００４】
しかし、近年、工業用水や下水道の取水水源等の有機物汚染により、用水処理における原水中には微生物代謝産物である高分子状のフミン酸やフルボ酸からなるＴＯＣ成分が増加している。このため、このような膜分離処理による前処理を行うシステムでは、前処理用のＭＦ膜やＵＦ膜の膜面に、原水中のＴＯＣ成分である高分子状のフミン酸やフルボ酸が吸着ないし沈着して膜を汚染させ、膜の濾過抵抗を高める傾向が増々強くなってきている。このような高分子状のフミン酸やフルボ酸による膜汚染が生じた場合には、ＭＦ膜やＵＦ膜の洗浄法として一般的な水逆洗では除去できず、薬品洗浄を行う必要がある。
【０００５】
また、排水処理設備において、下水や産業排水の生物処理水を処理して再利用する場合においても、その生物処理水中には微生物代謝産物であるフミン酸やフルボ酸からなるＴＯＣ成分が存在するため、上記と同様な問題があった。
【０００６】
本発明者は、このような原水中のＴＯＣ成分である高分子状のフミン酸やフルボ酸によるＭＦ膜やＵＦ膜の膜汚染の問題を解決すべく研究を重ねた結果、これらの膜の前段でオゾン処理を実施することにより、膜汚染を防止することができることを見出した。即ち、オゾン処理によりこれら高分子状のフミン酸やフルボ酸を分解することにより、原水中の高分子成分を減少させてＭＦ膜やＵＦ膜の有機物汚染を抑制させることができる。また、オゾン共存下でＭＦ膜やＵＦ膜に通水することにより、膜面に沈着したこれらの汚染物を酸化分解させることもでき、常に清浄な膜面を保つことで、膜の透過流束を高く維持することができる。
【０００７】
しかして、本発明者はこのようなオゾン共存下でＭＦ膜やＵＦ膜に通水する装置において、より一層安定かつ効率的な処理を行うべく、膜の透過水の残留オゾン濃度を検出し、その値に基いてオゾン注入量を制御する方式を先に提案した（特願平１０−８６１００号）。
【０００８】
【発明が解決しようとする課題】
このようにオゾンを注入してオゾンにより原水中のＴＯＣ成分を酸化分解する場合、具体的なオゾンの注入方法としては、膜分離装置の前段にオゾン反応塔を設ける方法や、膜分離装置への原水導入部に直接オゾンガスを供給する方法などが考えられるが、それぞれ一長一短があり、必ずしも満足し得るものではない。
【０００９】
即ち、膜分離装置の前段にオゾン反応塔を設ける方法では、オゾン酸化時間を十分に確保することができるため、原水中のＴＯＣ成分である高分子状のフミン酸やフルボ酸の分解効率が高いが、オゾン反応塔を必要とし、装置設備が大型化する。
【００１０】
また、膜分離装置への原水導入部に直接オゾンガスを供給する方法では、オゾン反応塔は不要であるが、オゾン酸化時間が短く、原水中のＴＯＣ成分の分解が不十分となり、後段の設備、例えば活性炭吸着塔の負荷を増大するなどの問題がある。
【００１１】
本発明は上記従来の問題点を解決し、膜汚染の防止のために原水をオゾン酸化処理した後、膜分離処理する用排水処理装置において、オゾン反応塔を設けることなく、オゾンの吸収効率及びオゾンによる原水中のＴＯＣ成分の酸化分解効率を高め、長期に亘り膜分離装置を安定かつ効率的に運転することができる用排水処理装置を提供することを目的とする。
【００１２】
【課題を解決するための手段】
本発明の用排水処理装置は、原水槽と、膜分離装置と、オゾン注入手段とを備えた用排水処理装置であって、該オゾン注入手段は、原水槽から膜分離装置へ原水を送給するための原水送給配管と、膜分離装置の濃縮水を原水槽に戻すための濃縮水戻り配管とにオゾンを供給可能であると共に、オゾン注入点の切り換え手段を備え、該オゾン注入点の切り換え手段は、原水のＴＯＣ成分量が低い場合の膜分離工程においては、原水送給配管のみにオゾン注入し、原水のＴＯＣ成分量が高い場合の膜分離工程においては、原水送給配管及び濃縮水戻り配管にオゾン注入し、逆洗工程においては、濃縮水戻り配管のみにオゾン注入するようにオゾン注入点を切り換える手段であることを特徴とする。
【００１３】
本発明の用排水処理装置では、オゾンガスを原水送給配管及び濃縮水戻り配管に直接注入することにより次のような作用が奏される。これにより、オゾン反応塔を設けることなくオゾンの吸収効率及びオゾンによるＴＯＣ成分の酸化分解効率を高めることができる。
【００１４】
▲１▼ 原水送給配管に直接オゾンガスを注入すると共に、濃縮水戻り配管でもオゾンガスを注入することにより、オゾンガスを原水槽にて再吸収させることができる。
▲２▼ 膜分離装置で必須な逆洗操作等、原水が膜分離装置に供給されない工程ないし期間において、オゾンガスの供給を停止することなく、オゾン注入点を切り換え、濃縮水戻り配管にオゾンガスを注入することにより、膜分離処理の運転停止中もオゾンによる酸化分解を継続させることができる。
▲３▼ 上記▲２▼より、膜分離処理を再開した時点で、原水のオゾン酸化が進行しており、膜汚染物質である高分子状のフミン酸やフルボ酸の分解が進んだ原水を膜分離装置に供給できるため、膜汚染を低減させることができる。
▲４▼ 逆洗工程等で膜面のフラッシングを原水を用いて行う場合にも、逆洗工程中にオゾンガスが原水槽に供給され、原水のオゾン酸化を進行させることとなるため、フラッシング原水からの膜面の汚染を防止することができる。
▲５▼ 有機物濃度が高く、オゾン消費量が大きい原水を対象とし、オゾン注入量を増加させる必要がある場合でも、原水送給配管と濃縮水戻り配管との両方にオゾンガスを注入することで容易に対処できる。
【００１５】
本発明の用排水処理装置では、濃縮水戻り配管の末端は、原水槽内の保有原水中に位置することが好ましく、これにより、原水槽をオゾン反応槽として機能させてより一層オゾンの吸収効率を高めることができる。
【００１６】
【発明の実施の形態】
以下に図面を参照して本発明の実施の形態を詳細に説明する。
【００１７】
図１は本発明の用排水処理装置の実施の形態を示す系統図である。
【００１８】
この用排水処理装置で原水の処理を行うには、バルブＶ₁を開、バルブＶ₂を閉としてポンプＰを作動させる。配管１１より導入された原水は、原水槽１を経て配管（原水送給配管）１２より膜分離装置２に導入され、不溶物が固液分離される。この膜分離装置２の濃縮水は循環水として配管（濃縮水戻り配管）１３より原水槽１に戻され、透過水は処理水として配管１４より取り出される。
【００１９】
このような膜分離処理において、オゾン発生器３からのオゾンガスが配管３Ａ，３Ｂより配管１２及び配管１３にそれぞれ注入されており、原水は配管１２において膜分離処理に先立ちオゾンガスが注入され、膜分離処理後、オゾンガスが注入された濃縮水が原水槽１に循環される過程で更にオゾンガスが注入されることで、効率的なオゾンの吸収及びＴＯＣ成分の酸化分解が行われる。
【００２０】
原水送給配管である配管１２にオゾンガスを注入する位置は、図示の如く、原水ポンプＰの入口側とするのが、オゾンガスの注入効率の面で好ましい。また、同様にオゾンガスの注入効率の面から、濃縮水戻り配管である配管１３にオゾンガスを注入する位置は、図示の如く、原水槽１に直結する垂直配管部分とするのが好ましい。
【００２１】
図示の用排水処理装置では、この配管１３の排出側の先端は原水槽１の保有原水中で開口している。このように配管１３の開口を原水槽１の保有原水中に設けることにより、原水槽１をオゾン反応塔として機能させることができ、好ましい。
【００２２】
なお、原水槽をオゾン反応塔として機能させる場合、原水槽は、その上部にラシヒリング等の充填層を設け、この充填層の上方に散水機構を設けた構成としても良い。
【００２３】
ところで、膜分離装置２では、膜分離処理を継続して行うことにより膜面に汚染物が付着して膜の透過流束が低下してくる。この場合には、ポンプＰを停止して、自動弁Ｖ₁を閉、自動弁Ｖ₂を開とし、逆洗水を配管１５より膜分離装置２に導入して配管１６より逆洗排水を排出することにより膜面の逆流洗浄を行う。この逆洗期間中は、オゾンガスを配管１３にのみ注入し、原水槽１にオゾンガスを供給することで、逆洗期間中においてもオゾンの吸収及びＴＯＣ成分の酸化分解を促進することができる。
【００２４】
また、原水中のＴＯＣ成分量が少ない場合には、膜分離処理工程においては、原水送給配管である配管１２にのみオゾンガスを注入し、逆洗工程においては濃縮水戻り配管である配管１３にのみオゾンガスを注入するようにオゾンガス注入点を切り換える。この場合、オゾンガスを注入する配管３Ａ，３Ｂの分岐点に切り換え用の自動弁を設け、自動的にオゾン注入点を切り換えるようにすることもできる。
【００２５】
なお、膜分離装置２の膜種としては、ＭＦ膜、ＵＦ膜等を用いることができ、本発明においては、図１に示す如く濃縮水の循環経路を有するクロスフロー方式で処理を行う。
【００２６】
この膜分離装置２には、オゾンガスを含む水が流入するため、膜分離装置２の膜の材質としては、ガラスやアルミナ系のセラミック素材、金属製素材から構成される無機膜や、有機膜にあっては、四フッ化ポリエチレンや二フッ化ポリビニリデン等のフッ素系素材やポリエーテルエーテルケトン等のオゾン耐食性の強いものを用いるのが好ましい。
【００２７】
膜分離装置２の透過水は、残留オゾンの除去、その他、膜分離装置２で除去し得なかった残留不純物の除去を目的として、更に活性炭吸着塔に通水して処理しても良い。
【００２８】
【発明の効果】
以上詳述した通り、本発明の用排水処理装置によれば、膜汚染の防止のために原水をオゾン酸化処理した後、膜分離処理する用排水処理装置において、オゾン反応塔を設けることなく、オゾンを原水に効率的に吸収させて、オゾンによる原水中のＴＯＣ成分の酸化分解効率を高め、安定かつ効率的な膜分離装置の運転を長期に亘り継続して行うことができる。
【図面の簡単な説明】
【図１】本発明の用排水処理装置の実施の形態を示す系統図である。
【符号の説明】
１原水槽
２膜分離装置
３オゾン発生器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment apparatus for subjecting raw water to ozone oxidation treatment and membrane separation treatment of ozone treated water.
[0002]
[Prior art and prior art]
Conventionally, as a pretreatment system for purification equipment such as reverse osmosis (RO) membrane separators in water or wastewater treatment, a system comprising agglomeration, sedimentation and sand filtration has been generally adopted. Then, when the organic matter concentration of raw | natural water increases, there exists a fault that it is necessary to add a coagulant | flocculant, such as ferric chloride, polyaluminum chloride, and aluminum sulfate, in large quantities. In addition, it is necessary to adjust the addition amount of the flocculant corresponding to the water quality fluctuation of the raw water, and there is also a problem that the quality of the treated water is deteriorated when appropriate addition amount control is not performed.
[0003]
For this reason, membrane separation processing using a microfiltration (MF) membrane, an ultrafiltration (UF) membrane, or the like has been adopted instead of such a conventional pretreatment process. According to the MF membrane and UF membrane, colloidal components that contaminate the subsequent RO membrane can be removed without adding a flocculant or only by adding a small amount of flocculant, thereby suppressing contamination of the RO membrane. Thus, the chemical cleaning interval can be extended and the operation of the RO membrane separator can be made more efficient.
[0004]
However, in recent years, due to organic contamination such as industrial water and sewer intake water sources, TOC components consisting of polymeric humic acids and fulvic acids, which are microbial metabolites, are increasing in raw water in the water treatment. For this reason, in such a system for pretreatment by membrane separation treatment, polymer humic acid or fulvic acid, which is a TOC component in raw water, is not adsorbed on the membrane surface of the MF membrane or UF membrane for pretreatment. There is an increasing tendency to deposit and contaminate the membrane and increase the filtration resistance of the membrane. When membrane contamination due to such a polymeric humic acid or fulvic acid occurs, it cannot be removed by a general water backwashing method for cleaning the MF membrane or UF membrane, and it is necessary to perform chemical cleaning.
[0005]
In addition, even when wastewater treatment facilities treat and reuse biological treated water such as sewage and industrial wastewater, the biologically treated water contains TOC components composed of humic acid and fulvic acid that are microbial metabolites. There was a problem similar to the above.
[0006]
The present inventor conducted research to solve the problem of membrane contamination of the MF membrane and UF membrane due to the polymer humic acid and fulvic acid that are TOC components in the raw water. The present inventors have found that film contamination can be prevented by performing ozone treatment. That is, by decomposing these polymeric humic acids and fulvic acids by ozone treatment, the polymer components in the raw water can be reduced, and organic matter contamination of the MF film and UF film can be suppressed. In addition, by passing water through the MF membrane and UF membrane in the presence of ozone, these contaminants deposited on the membrane surface can be oxidatively decomposed. By always maintaining a clean membrane surface, the permeation flux of the membrane Can be kept high.
[0007]
Therefore, the present inventor detects the residual ozone concentration of the permeated water of the membrane in order to perform more stable and efficient treatment in the apparatus that allows water to pass through the MF membrane and UF membrane in the presence of ozone, A method for controlling the ozone injection amount based on the value was previously proposed (Japanese Patent Application No. 10-86100).
[0008]
[Problems to be solved by the invention]
When ozone is injected and TOC components in raw water are oxidatively decomposed by ozone as described above, specific ozone injection methods include a method of providing an ozone reaction tower in front of the membrane separator, Although a method of supplying ozone gas directly to the raw water introduction part is conceivable, there are merits and demerits, respectively, which are not always satisfactory.
[0009]
That is, in the method in which the ozone reaction tower is provided in the front stage of the membrane separation apparatus, the ozone oxidation time can be sufficiently secured, so that the decomposition efficiency of the polymeric humic acid and fulvic acid that are TOC components in the raw water is high However, an ozone reaction tower is required, and the equipment becomes larger.
[0010]
In addition, in the method of supplying ozone gas directly to the raw water introduction part to the membrane separator, an ozone reaction tower is unnecessary, but the ozone oxidation time is short, the decomposition of the TOC component in the raw water becomes insufficient, For example, there is a problem of increasing the load of the activated carbon adsorption tower.
[0011]
The present invention solves the above-mentioned conventional problems, and in a wastewater treatment apparatus for membrane separation treatment after raw water is subjected to ozone oxidation treatment to prevent membrane contamination, ozone absorption efficiency and An object of the present invention is to provide a wastewater treatment apparatus for improving the oxidative decomposition efficiency of TOC components in raw water by ozone and capable of operating the membrane separation apparatus stably and efficiently over a long period of time.
[0012]
[Means for Solving the Problems]
The wastewater treatment apparatus of the present invention is a wastewater treatment apparatus provided with a raw water tank, a membrane separation device, and an ozone injection means, and the ozone injection means feeds raw water from the raw water tank to the membrane separation apparatus. Ozone can be supplied to the raw water supply pipe for supplying the concentrated water of the membrane separator and the concentrated water return pipe for returning the concentrated water of the membrane separator to the raw water tank, and provided with means for switching the ozone injection point. In the membrane separation process when the raw water TOC component amount is low, ozone is injected only into the raw water supply pipe, and in the membrane separation step when the raw water TOC component amount is high, the raw water supply pipe and the concentration are switched. Ozone is injected into the water return pipe, and in the backwash process, the ozone injection point is switched so that ozone is injected only into the concentrated water return pipe .
[0013]
In the wastewater treatment apparatus of the present invention, the following effects are exhibited by directly injecting ozone gas into the raw water supply pipe and the concentrated water return pipe. Thereby, the absorption efficiency of ozone and the oxidative decomposition efficiency of the TOC component by ozone can be improved without providing an ozone reaction tower.
[0014]
(1) The ozone gas can be reabsorbed in the raw water tank by injecting ozone gas directly into the raw water supply pipe and also injecting ozone gas into the concentrated water return pipe.
(2) In the process or period when raw water is not supplied to the membrane separator, such as the backwash operation that is essential for the membrane separator, the ozone injection point is switched and the ozone gas is injected into the concentrated water return pipe without stopping the supply of ozone gas. By doing so, oxidative decomposition by ozone can be continued even when the operation of the membrane separation treatment is stopped.
(3) From the above (2), when the membrane separation treatment is resumed, ozone oxidation of the raw water has progressed, and the raw water that has been decomposed by the polymeric humic acid and fulvic acid, which are membrane contaminants, is converted into a membrane. Since it can supply to a separation apparatus, membrane contamination can be reduced.
(4) Even when the membrane surface is flushed with raw water in the backwashing process, etc., ozone gas is supplied to the raw water tank during the backwashing process and the ozone oxidation of the raw water proceeds. It is possible to prevent contamination of the film surface.
(5) For raw water with high organic matter concentration and large ozone consumption, even if it is necessary to increase the amount of ozone injection, it is easy by injecting ozone gas into both the raw water supply pipe and the concentrated water return pipe Can be dealt with.
[0015]
In the wastewater treatment apparatus for use in the present invention, the end of the concentrated water return pipe is preferably located in the retained raw water in the raw water tank, thereby allowing the raw water tank to function as an ozone reaction tank and further absorbing efficiency of ozone. Can be increased.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a system diagram showing an embodiment of the waste water treatment apparatus of the present invention.
[0018]
To perform processing of the raw water in the use waste water treatment apparatus, the valve V ₁ opened, actuating the pump P and the valve V ₂ is closed. The raw water introduced from the pipe 11 passes through the raw water tank 1 and is introduced from the pipe (raw water feed pipe) 12 to the membrane separation device 2 to separate the insoluble matter into solid and liquid. The concentrated water of the membrane separation device 2 is returned to the raw water tank 1 from a pipe (concentrated water return pipe) 13 as circulating water, and the permeated water is taken out from the pipe 14 as treated water.
[0019]
In such a membrane separation process, ozone gas from the ozone generator 3 is injected into the pipe 12 and the pipe 13 from the pipes 3A and 3B, respectively, and the raw water is injected with ozone gas in the pipe 12 prior to the membrane separation process. After the treatment, ozone gas is further injected while the concentrated water into which the ozone gas has been injected is circulated to the raw water tank 1, thereby efficiently absorbing ozone and oxidatively decomposing TOC components.
[0020]
As shown in the figure, the position where ozone gas is injected into the pipe 12 which is the raw water supply pipe is preferably on the inlet side of the raw water pump P from the viewpoint of ozone gas injection efficiency. Similarly, from the viewpoint of ozone gas injection efficiency, it is preferable that the position where ozone gas is injected into the pipe 13 which is the concentrated water return pipe is a vertical pipe portion directly connected to the raw water tank 1 as shown in the figure.
[0021]
In the illustrated waste water treatment apparatus, the tip of the pipe 13 on the discharge side is open in the raw water retained in the raw water tank 1. Thus, by providing the opening of the pipe 13 in the retained raw water of the raw water tank 1, the raw water tank 1 can function as an ozone reaction tower, which is preferable.
[0022]
In addition, when making a raw | natural water tank function as an ozone reaction tower, the raw | natural water tank is good also as a structure which provided the filling layer, such as a Raschig ring, in the upper part, and provided the watering mechanism above this packed bed.
[0023]
By the way, in the membrane separation apparatus 2, when the membrane separation process is continuously performed, contaminants adhere to the membrane surface and the permeation flux of the membrane decreases. In this case, the pump P is stopped, the automatic valve V ₁ is closed, the automatic valve V ₂ is opened, backwash water is introduced into the membrane separation device 2 from the pipe 15, and the backwash drainage is discharged from the pipe 16. By doing so, the membrane surface is back-flow cleaned. During the backwashing period, ozone gas is injected only into the pipe 13 and the ozone gas is supplied to the raw water tank 1, so that the absorption of ozone and the oxidative decomposition of the TOC component can be promoted even during the backwashing period.
[0024]
Further, when the amount of TOC component in the raw water is small, ozone gas is injected only into the pipe 12 that is the raw water supply pipe in the membrane separation process, and into the pipe 13 that is the concentrated water return pipe in the backwash process. only Ru switched ozone gas injection point to inject ozone gas. In this case, an automatic valve for switching may be provided at the branch point of the piping 3A, 3B for injecting ozone gas so that the ozone injection point is automatically switched.
[0025]
As the membrane type of the membrane separation device 2, an MF membrane, a UF membrane, or the like can be used. In the present invention, the treatment is performed by a cross flow system having a circulation path of concentrated water as shown in FIG.
[0026]
Since water containing ozone gas flows into the membrane separation device 2, the material of the membrane of the membrane separation device 2 may be an inorganic membrane made of glass, an alumina-based ceramic material, or a metal material, or an organic membrane. In this case, it is preferable to use a fluorine-based material such as tetrafluoropolyethylene or polyvinylidene difluoride or a material having strong ozone corrosion resistance such as polyetheretherketone.
[0027]
The permeated water of the membrane separation device 2 may be further treated by passing water through an activated carbon adsorption tower for the purpose of removing residual ozone or other residual impurities that could not be removed by the membrane separation device 2.
[0028]
【The invention's effect】
As described in detail above, according to the wastewater treatment apparatus of the present invention, after the raw water is subjected to ozone oxidation treatment to prevent membrane contamination, the wastewater treatment apparatus for membrane separation treatment does not have an ozone reaction tower, Ozone can be efficiently absorbed into raw water to increase the oxidative decomposition efficiency of the TOC component in the raw water by ozone, and a stable and efficient operation of the membrane separation apparatus can be continuously performed over a long period of time.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a waste water treatment apparatus of the present invention.
[Explanation of symbols]
1 Raw water tank 2 Membrane separation device 3 Ozone generator

Claims

A wastewater treatment apparatus comprising a raw water tank, a membrane separation device, and an ozone injection means,
The ozone injection means can supply ozone to a raw water supply pipe for feeding raw water from the raw water tank to the membrane separation apparatus and a concentrated water return pipe for returning the concentrated water of the membrane separation apparatus to the raw water tank. There is also a means for switching the ozone injection point,
The ozone injection point switching means is:
In the membrane separation process when the amount of raw water TOC component is low, ozone is injected only into the raw water supply pipe,
In the membrane separation process when the amount of raw water TOC component is high, ozone is injected into the raw water supply pipe and concentrated water return pipe ,
In the backwashing process, the wastewater treatment apparatus according to claim 1, which is means for switching an ozone injection point so that ozone is injected only into the concentrated water return pipe .

Position of the switching means of the ozone injection point, according to claim 1, wherein a branch point of the pipe for injecting the ozone gas into the return concentrated water pipe and the pipe for injecting the ozone gas raw water feed pipe Wastewater treatment equipment for