JP2008302333A - Method and apparatus for production of fresh water - Google Patents

Method and apparatus for production of fresh water Download PDF

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JP2008302333A
JP2008302333A JP2007153612A JP2007153612A JP2008302333A JP 2008302333 A JP2008302333 A JP 2008302333A JP 2007153612 A JP2007153612 A JP 2007153612A JP 2007153612 A JP2007153612 A JP 2007153612A JP 2008302333 A JP2008302333 A JP 2008302333A
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membrane
water
reverse osmosis
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osmosis membrane
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Shinichi Yoshikawa
慎一 吉川
Masato Onishi
真人 大西
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Hitachi Plant Technologies Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To prevent a deterioration in the membrane separation performance of the reverse osmosis membrane by removing a soluble organic matter in water to be treated and thereby attempt during long-period stabilization of the membrane separation performance. <P>SOLUTION: A fresh water producing method is characterized by filtering target water, e.g. biologically reactive water or marine water mixed with sewage, with a reverse osmosis membrane so as to remove ions in the target water. After having passed through a ceramic-made nano-filter-membrane 14, as a pretreatment of the reverse osmosis membrane 12, to remove soluble organic matter, the target water is passed through the reverse osmosis membrane 12 to remove ions in the target water. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は造水方法及びその装置に関し、特に逆浸透膜（ＲＯ膜）を用いた造水方法及びその装置に関する。   The present invention relates to a fresh water generation method and an apparatus therefor, and more particularly to a fresh water generation method using a reverse osmosis membrane (RO membrane) and an apparatus therefor.

造水及び水処理に用いられる膜には、精密ろ過膜（ＭＦ膜）、限外ろ過膜（ＵＦ膜）、ナノろ過膜（ＮＦ膜）、逆浸透膜（ＲＯ膜）がある。
このうち逆浸透膜は孔径が最も小さく、水中に溶解している塩類、有機物等を除去し、水だけを通すことができる分離膜であり、脱塩分野、食品分野、半導体分野で多用されている。 Membranes used for water production and water treatment include microfiltration membranes (MF membranes), ultrafiltration membranes (UF membranes), nanofiltration membranes (NF membranes), and reverse osmosis membranes (RO membranes).
Of these, reverse osmosis membranes have the smallest pore size and can remove salts and organic substances dissolved in water, allowing only water to pass through. Reverse osmosis membranes are widely used in the desalting, food, and semiconductor fields. Yes.

逆浸透膜は上述のように塩類、有機物等を除去して真水などの処理水を得ることができるが、膜ろ過分離によって膜表面に塩類などの無機物や、有機物が付着し、膜が汚染されて膜の透水量が減少したり、ろ過圧力が上昇するなどの性能の低下が生じる。そのため、この汚染を除去する洗浄作業が必要となる。この洗浄作業は無機物と有機物で異なっている。例えば無機物の洗浄には水洗いまたは酸洗いを行い、有機物の場合には酸化剤を用いて洗浄している。ところが逆浸透膜は、洗浄回数の増加、または特に強い酸化剤を用いて洗浄するとろ過膜が劣化し易く、膜寿命が低下するという問題があった。   As described above, reverse osmosis membranes can obtain treated water such as fresh water by removing salts, organic substances, etc., but membrane filtration separates inorganic substances such as salts and organic substances on the membrane surface and contaminates the membrane. As a result, the water permeability of the membrane decreases and the performance drops such as an increase in filtration pressure. For this reason, a cleaning operation for removing this contamination is required. This cleaning operation is different for inorganic and organic substances. For example, the inorganic material is washed with water or pickling, and the organic material is washed with an oxidizing agent. However, the reverse osmosis membrane has a problem that when the number of washings is increased, or when the membrane is washed with a particularly strong oxidizing agent, the filtration membrane is liable to deteriorate, and the membrane life is reduced.

そこで逆浸透膜の膜ろ過の汚染の負荷を軽減する目的で膜ろ過分離の前処理として例えば（１）〜（３）に示す方法によって、予め有機性廃水の有機物や塩類を除去して逆浸透膜のろ過膜の汚染を低減することが行われている。
（１）被処理水に塩素を間欠的に添加してバイオファウリングを防止する。
被処理水中の懸濁物質が膜表面に付着するバイオファウリングが起こる。そうすると逆浸透膜のろ過性能が著しく低下してしまう。特許文献１には、逆浸透膜の前処理方法において間欠的に被処理水に塩素系滅菌剤を注入する処理方法が開示されている。
（２）逆浸透膜の前段にナノろ過膜を用いてイオン除去する。
特許文献２には、海水をナノろ過膜に通して硫酸イオン濃度を低下させて、ついで逆浸透膜に通して塩類を除去する淡水化方法が開示されている。
（３）有機物除去のために前処理として生物処理を行う。
特許文献３の水処理方法によれば、逆浸透膜処理の前段に生物処理槽を設け、被処理水を生物処理することで同化可能有機炭素濃度を制御し、逆浸透膜に供している。
特開平６−２３３５６号公報 特開平９−１４１２６０号公報 特開２００３−１１２１８１号公報 Therefore, reverse osmosis is performed by removing organic substances and salts in advance from the organic wastewater by the method shown in (1) to (3) as a pretreatment of membrane filtration separation for the purpose of reducing the load of membrane filtration contamination of the reverse osmosis membrane. It has been done to reduce the contamination of the membrane filtration membrane.
(1) Chlorine is intermittently added to water to be treated to prevent bio-fouling.
Biofouling occurs in which suspended substances in the water to be treated adhere to the membrane surface. If it does so, the filtration performance of a reverse osmosis membrane will fall remarkably. Patent Document 1 discloses a treatment method in which a chlorine-based sterilant is intermittently injected into water to be treated in a pretreatment method for a reverse osmosis membrane.
(2) Ion removal using a nanofiltration membrane before the reverse osmosis membrane.
Patent Document 2 discloses a desalination method in which seawater is passed through a nanofiltration membrane to reduce the sulfate ion concentration and then passed through a reverse osmosis membrane to remove salts.
(3) A biological treatment is performed as a pretreatment for removing organic substances.
According to the water treatment method of Patent Document 3, a biological treatment tank is provided in the previous stage of the reverse osmosis membrane treatment, and the concentration of assimilable organic carbon is controlled by biologically treating the water to be treated, which is used for the reverse osmosis membrane.
JP-A-6-23356 JP-A-9-141260 JP 2003-112181 A

しかしながら、特許文献１に示す被処理水に塩素を添加する方法では、酸化剤である塩素によって逆浸透膜が次第に劣化してしまう。また塩素の添加により被処理水中の有機物と反応して有害なトリハロメタンが発生してしまう。薬品を添加すると塩類濃度が高まり、逆浸透膜における脱塩処理の負荷が増加してしまう。   However, in the method of adding chlorine to the water to be treated shown in Patent Document 1, the reverse osmosis membrane gradually deteriorates due to chlorine as an oxidizing agent. In addition, the addition of chlorine reacts with organic matter in the water to be treated and generates harmful trihalomethanes. Addition of chemicals increases the salt concentration and increases the load of desalting treatment in the reverse osmosis membrane.

また特許文献２に示すナノろ過膜を用いた場合では、逆浸透膜に生じていた無機物／有機物による汚染が前段のナノろ過膜で生じるだけであり、特許文献２で逆浸透膜の性能向上、寿命伸長が図れたとしても、前段のナノろ過膜のメンテナンス（洗浄・交換）に必要な時間、手間、費用を考慮するとシステム全体のメリットは乏しい。   In addition, in the case of using the nanofiltration membrane shown in Patent Document 2, the contamination by the inorganic / organic matter generated in the reverse osmosis membrane only occurs in the previous nanofiltration membrane. In Patent Document 2, the performance of the reverse osmosis membrane is improved. Even if the service life can be extended, the overall system benefits are poor considering the time, effort, and cost required for maintenance (cleaning and replacement) of the nanofiltration membrane in the previous stage.

さらに特許文献３に示す生物処理を行う方法では、被処理水に含まれる溶解性有機物が、活性汚泥の代謝などで生じた生物処理後のものである場合、一度生物処理を受けた有機物であるため、生物処理では非常に分解しにくい。よってＭＢＲ処理水、下水処理水混入水を被処理水とする場合には効果的でないという問題があった。   Furthermore, in the method of performing biological treatment shown in Patent Document 3, when the soluble organic matter contained in the water to be treated is after biological treatment produced by metabolism of activated sludge, it is an organic matter that has undergone biological treatment once. Therefore, it is very difficult to decompose by biological treatment. Therefore, there is a problem that it is not effective when MBR treated water or sewage treated water mixed water is treated water.

そこで本発明は、上記従来技術の問題点を解決するために逆浸透膜の膜分離性能の低下を防止し、膜分離性能の長期安定化を図ることを目的としている。   In view of the above, an object of the present invention is to prevent a decrease in the membrane separation performance of a reverse osmosis membrane and to stabilize the membrane separation performance for a long period of time in order to solve the above-mentioned problems of the prior art.

本発明の造水方法は、被処理水を逆浸透膜で膜ろ過し、被処理水中のイオンを除去する造水方法において、前記逆浸透膜の前処理として前記被処理水をセラミック製のナノろ過膜に通水して溶解性有機物を除去したのち、前記逆浸透膜に通水して前記被処理水に含まれるイオンを除去することを特徴としている。   The fresh water generation method of the present invention is a fresh water generation method in which water to be treated is subjected to membrane filtration with a reverse osmosis membrane to remove ions in the water to be treated. Water is passed through a filtration membrane to remove soluble organic matter, and then water is passed through the reverse osmosis membrane to remove ions contained in the water to be treated.

本発明の造水装置は、被処理水を逆浸透膜でろ過し、被処理水中のイオンを除去する造水装置において、前記逆浸透膜の前段に前記被処理水の溶解性有機物を除去するセラミック製のナノろ過膜と、前記セラミック製のナノろ過膜を通過した前記被処理水に含まれるイオンを除去する逆浸透膜とを備えたことを特徴としている。   The fresh water generator of the present invention removes soluble organic matter of the water to be treated before the reverse osmosis membrane in the fresh water generator that filters the water to be treated with a reverse osmosis membrane and removes ions in the water to be treated. It is characterized by comprising a ceramic nanofiltration membrane and a reverse osmosis membrane for removing ions contained in the water to be treated that has passed through the ceramic nanofiltration membrane.

上記構成による本発明の造水方法及びその装置によれば、逆浸透膜の前段に取り付けたセラミック製のナノろ過膜によって被処理水中に含まれる溶解性有機物を除去することができる。   According to the fresh water generation method and apparatus of the present invention having the above-described configuration, the soluble organic matter contained in the water to be treated can be removed by the ceramic nanofiltration membrane attached to the front stage of the reverse osmosis membrane.

これによりナノろ過膜の後段に取り付けた逆浸透膜への有機物の負荷が低減される。このため逆浸透膜の有機物による汚染が低減され酸化剤を用いたろ過膜の洗浄回数が少なくなり、ろ過膜の劣化を低減でき、逆浸透膜の長寿命化、及び膜分離性能の長期安定化を図ることができる。また本発明のナノろ過膜はセラミック製であるため、ろ過膜表面に付着した有機物を酸化剤で洗浄することにより容易に溶解性有機物を除去できる。このとき酸化剤によるろ過膜の劣化が起こらない。また強い酸化剤を用いて有機物を洗浄除去することができる。さらに本発明のナノろ過膜は、シリカイオン、カルシウムイオン、硫化物イオンなどのスケーリング成分を含む無機イオンを除去することがないため、スケーリングや無機成分により膜の汚染がない。そのためナノろ過膜の洗浄は有機物の除去のみを考慮すればよい。   Thereby, the load of the organic substance to the reverse osmosis membrane attached to the latter stage of the nanofiltration membrane is reduced. For this reason, contamination of the reverse osmosis membrane with organic substances is reduced, the number of cleaning of the filtration membrane using the oxidizing agent is reduced, the deterioration of the filtration membrane can be reduced, the life of the reverse osmosis membrane is extended, and the membrane separation performance is stabilized for a long time. Can be achieved. Further, since the nanofiltration membrane of the present invention is made of ceramic, the soluble organic matter can be easily removed by washing the organic matter adhering to the filtration membrane surface with an oxidizing agent. At this time, the membrane is not deteriorated by the oxidizing agent. In addition, organic substances can be washed away using a strong oxidizing agent. Furthermore, since the nanofiltration membrane of the present invention does not remove inorganic ions including scaling components such as silica ions, calcium ions, and sulfide ions, there is no membrane contamination due to scaling or inorganic components. Therefore, it is only necessary to consider the removal of organic substances when cleaning the nanofiltration membrane.

また本発明の造水方法及びその装置は、逆浸透膜の前段に取り付けたセラミック製のナノろ過膜によって溶解性有機物を除去し、ついで逆浸透膜により無機物（イオン）を除去する。   Moreover, the fresh water generation method and apparatus of this invention remove a soluble organic substance with the ceramic nanofiltration membrane attached to the front | former stage of a reverse osmosis membrane, and remove an inorganic substance (ion) with a reverse osmosis membrane.

これにより逆浸透膜は主に被処理水中に含まれる無機物を除去する。逆浸透膜のろ過膜に付着した無機物は水洗い又は酸洗いで除去できるため、酸化剤洗浄に比べてろ過膜の劣化が少ない。よって逆浸透膜の長寿命化、及び膜分離性能の長期安定化を図ることができる。   Thereby, the reverse osmosis membrane mainly removes inorganic substances contained in the water to be treated. Since the inorganic substance adhering to the filtration membrane of the reverse osmosis membrane can be removed by washing with water or pickling, the filtration membrane is less deteriorated than that with oxidizing agent washing. Therefore, it is possible to extend the life of the reverse osmosis membrane and to stabilize the membrane separation performance for a long time.

また本発明のセラミック製のナノろ過膜は、公知技術の特許文献２とは異なり、有機物は除去するが、イオンは除去しない孔径であり、濃縮液のイオン濃度が高くなることによるスケーリングが生じることがない。従って、濃縮倍率を制限する必要がなく、全量ろ過での運転が可能である。これにより、通常のナノろ過膜の運転のようにクロスフローろ過をする必要がなく、クロスフローのための膜供給流量が不要であり、ポンプ容量を小さくでき、動力費も少なくてよい。   The ceramic nanofiltration membrane of the present invention has a pore size that removes organic matter but does not remove ions, unlike the known technology of Patent Document 2, and scaling occurs due to an increase in the concentration of ions in the concentrate. There is no. Therefore, there is no need to limit the concentration rate, and operation with total filtration is possible. Accordingly, it is not necessary to perform cross flow filtration as in the case of normal nanofiltration membrane operation, the membrane supply flow rate for cross flow is unnecessary, the pump capacity can be reduced, and the power cost can be reduced.

また本発明のセラミックナノろ過膜は、有機物が含まれていない水においてはカルシウムイオンを全く除去できないが、有機物、特にフミン質を含む被処理水では、カルシウムイオンを除去することが可能である。これはナノろ過膜の表面に蓄積した有機物、特にフミン質とカルシウムイオンが錯体を形成し、これによりカルシウムイオンが除去されるためである。よって後段の逆浸透膜で除去していた無機イオンの一部であるカルシウムイオンの負荷が軽減されて、ろ過膜の除去率が向上する。   The ceramic nanofiltration membrane of the present invention cannot remove calcium ions in water that does not contain organic substances, but can remove calcium ions in water to be treated containing organic substances, particularly humic substances. This is because organic substances accumulated on the surface of the nanofiltration membrane, in particular humic substances, and calcium ions form a complex, thereby removing calcium ions. Therefore, the load of calcium ions, which are some of the inorganic ions removed by the subsequent reverse osmosis membrane, is reduced, and the removal rate of the filtration membrane is improved.

本発明のナノろ過膜は、孔径が０．２〜２．０ｎｍであり分子量数１００〜数１０００の有機成分（溶解性、生物難溶解性、色度成分）を除去できる。従って被処理水中の有機物を凝集することなく直接ろ過しても除去することが可能であり、凝集剤やｐＨ調整剤などの薬剤が必要ない。このため薬品の投入による塩類濃度の増加がない。よって逆浸透膜の負荷を低減できる。   The nanofiltration membrane of the present invention has a pore size of 0.2 to 2.0 nm and can remove organic components (solubility, poor biological solubility, and chromaticity component) having a molecular weight of 100 to several thousand. Therefore, organic substances in the water to be treated can be removed by direct filtration without agglomeration, and agents such as an aggregating agent and a pH adjusting agent are not necessary. For this reason, there is no increase in salt concentration due to the introduction of chemicals. Therefore, the load on the reverse osmosis membrane can be reduced.

また本発明のナノろ過膜は、無機物を除去することなく透過させているので、膜表面に無機物が析出するスケーリングが生じない。このため、高圧をかけることなく低動力を維持できるとともに、濃縮水を低減して処理水の回収率を上げることができる。   Moreover, since the nanofiltration membrane of this invention is permeate | transmitting, without removing an inorganic substance, the scaling which an inorganic substance precipitates on the membrane surface does not arise. For this reason, while being able to maintain low power without applying a high pressure, it is possible to reduce the concentrated water and increase the recovery rate of the treated water.

本発明の造水方法及びその装置の実施形態を添付の図面を参照しながら以下詳細に説明する。
図１は本発明の造水装置の構成概略を示す図である。図示のように有機性廃水の造水装置１０は、被処理水が流入する逆浸透膜（ＲＯ膜）１２の上流側にナノろ過膜（ＮＦ膜）１４を取り付けている。 Embodiments of the fresh water generation method and apparatus of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of a fresh water generator of the present invention. As shown in the figure, the organic wastewater desalination apparatus 10 has a nanofiltration membrane (NF membrane) 14 attached upstream of a reverse osmosis membrane (RO membrane) 12 into which treated water flows.

本発明の被処理水としては、例えば、下水又は工業廃水を活性汚泥による生物反応処理を行った処理後の生物反応処理水や、下水又は下水処理水が混合した海水など、いずれも溶解性有機物含有水を対象としている。ここで溶解性有機物とは、例えば色度成分がある。色度成分はフルボ酸、フミン酸などのフミン質で分子量が数万以下であり、処理水中の色度として残存するものである。また活性汚泥による生物反応処理を行った処理後の生物反応処理水中の溶解性有機物は、生物処理後の活性汚泥の代謝物などである。このため生物処理では非常に分解しにくいものである。   As treated water of the present invention, for example, biological reaction treated water after biological reaction treatment of sewage or industrial wastewater by activated sludge, seawater mixed with sewage or sewage treated water, all soluble organic matter It contains water. Here, the soluble organic substance includes, for example, a chromaticity component. The chromaticity component is a humic substance such as fulvic acid or humic acid, has a molecular weight of tens of thousands or less, and remains as chromaticity in the treated water. The soluble organic matter in the biological reaction treated water after the biological reaction treatment with activated sludge is a metabolite of the activated sludge after biological treatment. For this reason, it is very difficult to decompose by biological treatment.

逆浸透膜１２は、孔径が最も小さい膜であり、一般に用いられる膜素材としてポリアミド系、アミド系、酢酸セルロース系などがあげられる。また逆浸透膜１２の形状は、一例として活性層、支持層、基材からなる複合膜をスパイラル型構造に形成したものを用いることができる。逆浸透膜１２は、被処理水に溶解している塩類や有機物等を除去し、水だけを通すことができる。このとき処理水のほか、塩類、有機物や不純物などの濃縮水が常に連続的に排出される。   The reverse osmosis membrane 12 is a membrane having the smallest pore diameter, and examples of generally used membrane materials include polyamide, amide, and cellulose acetate. As the shape of the reverse osmosis membrane 12, for example, a composite membrane comprising an active layer, a support layer, and a base material formed in a spiral structure can be used. The reverse osmosis membrane 12 can remove salts and organic substances dissolved in the water to be treated and allow only water to pass through. At this time, in addition to the treated water, concentrated water such as salts, organic substances and impurities is continuously discharged.

ナノろ過膜１４は、逆浸透膜１２よりも孔径が大きく、イオン類の除去率は大きくはないが、分子量数百程度以上の有機物を分離し除去することができる。一般に用いられているナノろ過膜は、膜素材としてポリアミド（ＰＡ）、ポリビニルアルコール（ＰＶＡ）、酢酸セルロース（ＣＡ）などが用いられている。これらの膜素材は、酸化剤によるろ過膜の洗浄処理によって劣化し易い問題がある。   The nanofiltration membrane 14 has a larger pore size than the reverse osmosis membrane 12 and does not have a high ion removal rate, but can separate and remove organic substances having a molecular weight of several hundreds or more. Generally used nanofiltration membranes include polyamide (PA), polyvinyl alcohol (PVA), cellulose acetate (CA) and the like as membrane materials. These membrane materials have a problem that they are easily deteriorated by the cleaning treatment of the filtration membrane with an oxidizing agent.

そこで本発明のナノろ過膜１４は、セラミック製のナノろ過膜を用いている。セラミック製の細多孔膜は化学的、機械的、熱的に安定しているため、広範囲な用途性がある。以下セラミック製のナノろ過膜１４の製造方法について説明する。コーティングされた多層構造の最上層に厚さ２５０ｎｍで平均細孔サイズが５ｎｍのメソ多孔性のＴｉＯ２層を形成する。多層構造のコーティング後、ポリマーゲルが形成され、ついで室温で乾燥する。コーティングと乾燥の湿度調整は、ゲル網状組織の加水分解と縮合に影響しＮＦ膜の品質に依存している。湿度５０％以上でゲルの加水分解は縮合よりも速く促進し、その結果ＴｉＯ２・ｘＨ２Ｏ粒子が形成され、ついでメソ多孔性粒子管微細孔が形成される。乾燥後得られた膜を焼結する。これによりＴｉＯ２ナノろ過膜が形成される。 Therefore, the nanofiltration membrane 14 of the present invention uses a ceramic nanofiltration membrane. Ceramic microporous membranes have a wide range of applications because they are chemically, mechanically and thermally stable. Hereinafter, a method for manufacturing the ceramic nanofiltration membrane 14 will be described. A mesoporous TiO 2 layer having a thickness of 250 nm and an average pore size of 5 nm is formed on the top layer of the coated multilayer structure. After coating the multilayer structure, a polymer gel is formed and then dried at room temperature. The humidity control of coating and drying affects the hydrolysis and condensation of the gel network and depends on the quality of the NF membrane. At a humidity of 50% or higher, gel hydrolysis accelerates faster than condensation, resulting in the formation of TiO 2 .xH 2 O particles, followed by the formation of mesoporous particle tube micropores. The membrane obtained after drying is sintered. Thereby, a TiO 2 nanofiltration membrane is formed.

上記製法により得られたナノろ過膜は、材質として例えばＴｉＯ２、ＳｉＯ２、Ａｌ２Ｏ３を用い、孔径は０．２〜２．０ｎｍである。 The nanofiltration membrane obtained by the above production method uses, for example, TiO 2 , SiO 2 , or Al 2 O 3 as a material and has a pore diameter of 0.2 to 2.0 nm.

上記構成による有機性廃水の処理装置の廃水処理について以下説明する。本実施形態では一例として、活性汚泥による生物反応処理した後の処理水を逆浸透膜分離する場合について説明する。活性汚泥により生物反応処理された被処理水中には、生物処理後の活性汚泥の代謝物などの色度成分である溶解性有機物が含まれている。   The wastewater treatment of the organic wastewater treatment apparatus having the above configuration will be described below. In the present embodiment, as an example, a case will be described in which treated water after biological reaction treatment with activated sludge is subjected to reverse osmosis membrane separation. The treated water that has been subjected to biological reaction treatment with activated sludge contains soluble organic substances that are chromaticity components such as metabolites of activated sludge after biological treatment.

生物反応槽の排出側の配管上にはナノろ過膜１４、ついで逆浸透膜１２が設置されており、生物反応処理水（被処理水）は、まず始めにナノろ過膜１４に供給される。   A nanofiltration membrane 14 and then a reverse osmosis membrane 12 are installed on the discharge side pipe of the biological reaction tank, and biological reaction treated water (treated water) is first supplied to the nanofiltration membrane 14.

ナノろ過膜１４ではろ過膜で被処理水に含まれる溶解性有機物を除去する。そして塩類などの無機物はろ過膜の孔径よりも小さくろ過膜を通過する。ここで無機物に含まれるカルシウムイオンの一部は、ナノろ過膜除去され、ナノろ過膜上に付着した有機物のフミン質と錯体を形成し、除去される。   In the nanofiltration membrane 14, soluble organic substances contained in the water to be treated are removed by the filtration membrane. And inorganic substances, such as salts, pass through a filtration membrane smaller than the pore diameter of a filtration membrane. Here, a part of the calcium ions contained in the inorganic substance is removed by the nanofiltration membrane, and a complex with the humic substance of the organic matter attached on the nanofiltration membrane is removed.

ナノろ過膜１４を通過した被処理水は、ついで逆浸透膜１２に供給される。逆浸透膜１２では、被処理水に含まれる塩類などの無機物がろ過膜で除去される。ろ過膜を通過した水は処理水として再利用される。一方、ろ過膜で除去された塩類などの無機物は濃縮水として排出される。   The treated water that has passed through the nanofiltration membrane 14 is then supplied to the reverse osmosis membrane 12. In the reverse osmosis membrane 12, inorganic substances such as salts contained in the water to be treated are removed by the filtration membrane. The water that has passed through the filtration membrane is reused as treated water. On the other hand, inorganic substances such as salts removed by the filtration membrane are discharged as concentrated water.

このようにナノろ過膜で被処理水に含まれる溶解性有機物を除去するため、後段の逆浸透膜では、溶解性有機物の含有量が僅かとなる。このため有機物による汚染が減少し、酸化剤を用いた洗浄が低減される。またナノろ過膜では通常通過するカルシウムイオンの一部を除去することができる。   Thus, since the soluble organic substance contained in to-be-processed water is removed with a nanofiltration membrane, in the latter reverse osmosis membrane, content of a soluble organic substance becomes few. For this reason, contamination with organic substances is reduced, and cleaning with an oxidizing agent is reduced. Further, in the nanofiltration membrane, a part of the calcium ions that normally pass can be removed.

ところで所定期間膜ろ過分離を行ったナノろ過膜１４は、ろ過膜に付着した有機物を定期的に洗浄する必要がある。本発明のナノろ過膜は、セラミック製であるため、化学的に安定しており、酸化剤を用いた洗浄であっても、ろ過膜の劣化がほとんど起こらない。   By the way, the nanofiltration membrane 14 that has been subjected to membrane filtration separation for a predetermined period needs to periodically wash organic substances adhering to the filtration membrane. Since the nanofiltration membrane of the present invention is made of ceramic, it is chemically stable, and even when cleaning with an oxidizing agent is performed, the membrane is hardly deteriorated.

またナノろ過膜１４の後段に設けた逆浸透膜１２では、被処理水にほとんど溶解性有機物が含まれていないため、主に無機物を除去する。よって逆浸透膜１２の洗浄は水洗い又は酸洗いで洗浄することができる。このため酸化剤による洗浄回数が低減され、膜ろ過の劣化が低減される。   Further, in the reverse osmosis membrane 12 provided at the subsequent stage of the nanofiltration membrane 14, the inorganic water is mainly removed because the water to be treated contains almost no soluble organic matter. Therefore, the reverse osmosis membrane 12 can be washed with water or pickling. For this reason, the frequency | count of washing | cleaning by an oxidizing agent is reduced and deterioration of membrane filtration is reduced.

以上説明したように、本発明は逆浸透膜の前処理としてセラミック製のナノろ膜を取り付け、被処理水中に含まれる溶解性有機物を除去したのち、逆浸透膜で有機性廃水に含まれる無機物を除去している。これにより逆浸透膜への有機物の負荷を低減して酸化剤による膜洗浄の洗浄回数が低減される。ろ過膜の劣化を低減できるため、逆浸透膜の長寿命化、及び膜分離性能の長期安定化を図ることができる。   As described above, the present invention attaches a ceramic nanofiltration membrane as a pretreatment of the reverse osmosis membrane, removes the soluble organic matter contained in the water to be treated, and then contains the inorganic matter contained in the organic wastewater with the reverse osmosis membrane. Has been removed. Thereby, the load of the organic substance to the reverse osmosis membrane is reduced, and the number of times of membrane cleaning with an oxidizing agent is reduced. Since the deterioration of the filtration membrane can be reduced, the life of the reverse osmosis membrane can be extended and the membrane separation performance can be stabilized for a long time.

本発明は、下水を含む海水又は工業廃水を逆浸透膜分離処理して造水する分野等において有用である。   INDUSTRIAL APPLICABILITY The present invention is useful in fields such as seawater containing sewage or industrial wastewater to produce water by reverse osmosis membrane separation.

本発明の造水装置の構成概略を示す図である。It is a figure which shows the structure outline of the fresh water generator of this invention.

符号の説明Explanation of symbols

１０………造水装置、１２………逆浸透膜（ＲＯ膜）、１４………ナノろ過膜（ＮＦ膜）。 10 ............ Water generator, 12 ...... Reverse osmosis membrane (RO membrane), 14 ...... Nanofiltration membrane (NF membrane)

Claims (2)

被処理水を逆浸透膜で膜ろ過し、被処理水中のイオンを除去する造水方法において、
前記逆浸透膜の前処理として前記被処理水をセラミック製のナノろ過膜に通水して溶解性有機物を除去したのち、前記逆浸透膜に通水して前記被処理水に含まれるイオンを除去することを特徴とする造水方法。 In a fresh water generation method for removing ions in water to be treated by membrane filtering the water to be treated with a reverse osmosis membrane,
As the pretreatment of the reverse osmosis membrane, the water to be treated is passed through a ceramic nanofiltration membrane to remove soluble organic substances, and then the ions contained in the water to be treated are passed through the reverse osmosis membrane. A fresh water generation method characterized by removing. 被処理水を逆浸透膜でろ過し、被処理水中のイオンを除去する造水装置において、
前記逆浸透膜の前段に前記被処理水の溶解性有機物を除去するセラミック製のナノろ過膜と、
前記セラミック製のナノろ過膜を通過した前記被処理水に含まれるイオンを除去する逆浸透膜とを備えたことを特徴とする造水装置。 In a fresh water generator that filters the treated water through a reverse osmosis membrane and removes ions in the treated water,
A ceramic nanofiltration membrane that removes the soluble organic matter of the water to be treated before the reverse osmosis membrane;
A fresh water generator comprising a reverse osmosis membrane for removing ions contained in the water to be treated that has passed through the ceramic nanofiltration membrane.
JP2007153612A 2007-06-11 2007-06-11 Method and apparatus for production of fresh water Pending JP2008302333A (en)

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