JP3576314B2 - Sewage treatment method - Google Patents

Description

ここで、ａ，ｂは指定面（長方形）の２辺の長さ、Ｓは指定面の面積、ｆ（ｘ，ｙ）は指定面内での高さ、酢酸セルロ−スｏは次式で与えられる指定面の高さの平均値である。
【００１１】
【数２】

【００１２】
【発明の実施の形態】
以下、図面を参照しつつ本発明の実施の形態について説明する。
図１は本発明において使用する下水処理施設の一例を示している。
図１において、１は粗濾過装置であり、後続の処理施設に障害となる粗い浮遊物や油脂が除去され、スクリ−ン、沈砂池、油脂分離槽、ｐＨ調整槽等が設けられている。２は生物処理装置である。３は前処理装置であり、懸濁物質を除去し後置の逆浸透膜モジュ−ルを懸濁物質から保護するために設けられ、例えば、砂濾過装置や精密濾過装置が使用される。４は原水タンクを、５１は前段送液ポンプを、６１は原水に接する膜表面が酢酸セルロ−スで形成された前段の逆浸透膜モジュ−ルを、６１１は前段非透過水排出管を、６１２は前段透過水流出管をそれぞれ示している。
【００１３】
前段の酢酸セルロ−ス逆浸透膜モジュ−ルにおいては、酢酸セルロ−スがセルロ−スのエステルであり、アルカリによる加水分解劣化の問題があるから、原液のｐＨを３〜７程度に調整することが必要である。
図１において、４１は酸液タンクを、４２は原水タンク４内に酸液を注入するためのポンプをそれぞれ示し、ｐＨ計４３によりポンプが作動され、原水タンク４内のｐＨ値が５前後に調整される。
【００１４】
７は中間タンク、例えばパイプヘッダ−を、５２は後段送液ポンプを、６２は原水に接する膜表面が架橋芳香族ポリアミドで形成された後段の逆浸透膜モジュ−ルを、６２２は後段透過水流出管を、６２０は後段非透過水配管をそれぞれ示し、後段非透過水の一部が原水タンク４にリタ−ン管６２０’によりリタ−ンされ、残部は後段非透過水排出管６２１より排出され、後段透過水が後段透過水流出管６２２より用水として取り出されていく。８は必要に応じて設けられるアルカリ液タンクを、９は前段逆浸透膜分離モジュ−ル６１の透過側にアルカリ液を注入するためのポンプをそれぞれ示している。
【００１５】
上記施設を用いて本発明により下水を処理するには、下水を粗濾過装置１、生物処理装置２並びに前処理装置３で処理し、これを一旦原水タンク４に貯え、前段送液ポンプ５１により所定の圧力で前段逆浸透膜分離モジュ−ル６１に供給し、原水中の塩や有機物の通過の阻止により塩等の濃縮された非透過水を前段非透過水排出管６１１から排出し、透過側に所定の除去率で塩等を除去した透過水を発生させていく。
この場合、ポンプ４２により、酸、例えば、硫酸や塩酸を原水タンク４に注入してその原水のｐＨを５前後に調整する。
【００１６】
上記前段逆浸透膜分離モジュ−ル６１の前段透過水は一旦中間タンク７に貯え、必要に応じてポンプ９によりアリカリ液、例えば、水酸化ナトリウムや水酸化カリウム等を注入してその透過水のｐＨを調整し、このｐＨ調整透過水を送液ポンプ５２により所定の圧力で後段逆浸透膜分離モジュ−ル６２に供給し、塩の濃縮された後段非透過水の一部を前段ライン側にリタ−ンさせると共に後段非透過水の残部を後段非透過水排出管６２１から排出していく。後段逆浸透膜分離モジュ−ル６２により更に脱塩された後段透過水は、親水用水等の用水として使用していく。
上記において、後段逆浸透膜分離モジュ−ル６２の非透過水は全て排出し、前段ラインへのリタ−ン量を０にすることもできる。
【００１７】
上記後段液送ポンプを省略し、図２に示すように、前段逆浸透膜分離モジュ−ル６１のみならず後段逆浸透膜分離モジュ−ル６２の操作圧力をも前段液送ポンプ５１で発生させることもでき、この場合、前段逆浸透膜分離モジュ−ル６１はその透過側においても加圧されるので、透過側もこの加圧力に対処できる耐圧構造とされる。
なお、図２において、図１と同一符号は同一の構成要素を示している
上記前段及び後段の逆浸透膜分離モジュ−ルには、スパイラル型、中空糸型、チュ−ブラ−型、フレ−ム＆プレ−ト型等を使用できる。
上記において、逆浸透膜分離モジュ−ルには数台のモジュ−ルユニットを直列または並列に接続し、これらのユニット群の供給側を一括して原水供給管に接続し、透過側を一括して透過水流出管に接続したものも使用できる。
【００１８】
本発明が処理の対象とする下水中には、石鹸や洗剤排液のために多量の界面活性剤が含まれている。而るに、膜の表面層が酢酸セルロ−スで形成された逆浸透膜モジュ−ルにおいては、界面活性剤に接しても膜面への界面活性剤の吸着が殆ど観られずに透過流束の低下が僅かである。この界面活性剤は、比較的分子量が高く、前段の逆浸透膜モジュ−ルにより実質的にほぼ完全に遮断される。従って、前段逆浸透膜モジュ−ルによるほぼ完全な界面活性剤の遮断により、膜の表面層が架橋芳香族ポリアミドで形成された後段逆浸透膜モジュ−ルの界面活性剤接触下での低透過流束性を現出させずに、この後段逆浸透膜モジュ−ルに、窒素や燐に対する本来の高い塩除去率を効果的に発揮させ得、窒素や燐含有量が僅小で親水用水として利用可能な高水質の透過水を得ることができる。
【００１９】
【実施例】
〔実施例〕
前段の逆浸透膜モジュ−ルには、ｐＨ６．０、濃度０．２０％の食塩水を原水として２５℃、操作圧力２９．４ｋｇｆ／ｃｍ^２にて運転３０分後での食塩阻止率が９８％であり、膜が酢酸セルロ−スである日東電工株式会社製スパイラル型逆浸透膜モジュ−ルＮＴＲ−１６９８を使用した。
【００２０】
後段の逆浸透膜モジュ−ルには、ｐＨ６．５、濃度０．０５％の食塩水を原水として２５℃、操作圧力７．５ｋｇｆ／ｃｍ^２にて運転３０分後での食塩阻止率が９９．５％で、純水の透過流束が０．１３ｍ^３／ｍ^２・〔ｋｇｆ／ｃｍ^２〕・ｄａｙであり、膜が架橋芳香族ポリアミド系で、平均表面粗さが８０ｎｍの日東電工株式会社製スパイラル型逆浸透膜モジュ−ルを使用した。この逆浸透膜モジュ−ルの膜は、ポリスルホンからなる多孔質基材上に、ｍ−フェニレンジアミンを２．０重量％、ラウリル硫酸ナトリウムを０．１５重量％、トリエチルアミンを２．０重量％、カンファ−スルホン酸を４．０重量％、イソプロピルアルコ−ルを２０重量％含有した原液を接触させ、かくして形成した原液層に、トリメシン酸クロライドを０．１５重量％含有するヘキサン溶液を接触させ、その後１２０℃の熱風乾燥機で３分間保持して表面平均粗さ８０ｎｍの反応生成スキン層を形成したものである。
【００２１】
図１において（アルカリ液タンク８及びポンプ９は省略した）、亜硝酸窒素濃度５０ｐｐｍ、アンモニア性窒素濃度５０ｐｐｍ、燐濃度５０ｐｐｍで、洗剤を高濃度で含有し、ｐＨ値を６に調整した原水を原水タンク４に貯え、前段送液ポンプ５１の送液圧力を３０ｋｇｆ／ｃｍ^２、後段送液ポンプ５２の送液圧力を７．５ｋｇｆ／ｃｍ^２として、後段逆浸透膜モジュ−ル６２の初期透過流束を０．１３ｍ^３／ｍ^２・〔ｋｇｆ／ｃｍ^２〕・ｄａｙとするように運転し、その運転を２００時間継続した。
後段逆浸透膜モジュ−ル６２の透過水の水質は表１に示す通りであり、その透過水流量の経時的低下状態は図３に示す通りであった。
【００２２】
〔比較例１〕
実施例で前段逆浸透膜モジュ−ルとして使用した日東電工株式会社製スパイラル型逆浸透膜モジュ−ルのみを運転圧力３０ｋｇｆ／ｃｍ^２で運転して、実施例と同じ調整原水を処理した。初期透過流束は０．０３３ｍ^３／ｍ^２・〔ｋｇｆ／ｃｍ^２〕・ｄａｙであった。
この比較例での透過水の水質は表１に示す通りであり、その透過水流量の経時的低下状態は図３に示す通りであった。
【００２３】
〔比較例２〕
実施例で後段逆浸透膜モジュ−ルとして使用した日東電工株式会社製スパイラル型逆浸透膜モジュ−ルのみを運転圧力１０ｋｇｆ／ｃｍ^２で運転して、実施例と同じ調整原水を処理した。初期透過流束は０．０８ｍ^３／ｍ^２・〔ｋｇｆ／ｃｍ^２〕・ｄａｙであった。この比較例での透過水の水質は表１に示す通りであり、その透過水流量の経時的低下状態は図３に示す通りであった。
【００２４】
【表１】

【００２５】
表１から明らかなように、本発明に係る下水の処理方法によれば、下水に界面活性剤が多量に含有されていても、窒素並びに燐化合物を著しく微量にして処理でき、しかも、その透過流束も充分に大きくできるから、その処理水を用水として有効に利用できる。
【００２６】
【発明の効果】
本発明に係る下水の処理方法によれば、界面活性剤を実質的に遮断して架橋芳香族ポリアミド系逆浸透膜モジュ−ルの窒素や燐化合物に対する本来の優れた除去率、透過流束を有効に発揮させ得、下水に界面活性剤が多量に含有されていても、窒素並びに燐を著しく微量にして処理でき、しかも、その透過流束も充分に大きくできるから、その処理水を親水用水として、また水源への返送等により有効に利用できる。
【図面の簡単な説明】
【図１】本発明において使用する下水処理施設の一例を示す説明図である。
【図２】本発明において使用する下水処理施設の別例を示す説明図である。
【図３】本発明に係る実施例と比較例との経時的な透過流束特性を示す図表である。
【符号の説明】
１ 粗濾過装置
２ 生物処理装置
３ 前処理装置
４ 原水タンク
５１ 前段液送ポンプ
５２ 後段液送ポンプ
６１ 前段逆浸透膜モジュ−ル
６２ 後段逆浸透膜モジュ−ル
７ 中間タンク[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating sewage in which higher-order treatment is performed by membrane separation when treating sewage.
[0002]
[Prior art]
In urban sewage treatment, sewage is roughly filtered, biologically treated by an activated sludge method, and the treated water is discharged into rivers.
That is, the roughly filtered sewage is introduced into an aeration tank, and organic substances in the sewage are adsorbed and decomposed in an aerobic state by microorganisms in a suspended state, the microorganisms are proliferated, and the microorganism mixture (ML) in the aeration tank is finally purified. The microorganisms are led to the sedimentation basin, and the microorganisms are sedimented and separated. The microorganisms are returned to the sewage inflow section of the aeration tank as return sludge for circulation treatment, and excess sludge from the sedimentation basin is removed at appropriate times.
In recent years, for the purpose of environmental issues and effective use of water resources, it has been studied to reuse the treated water as water for use in public facilities such as parks without releasing the treated water. Therefore, for this effective use, it is necessary to remove nutrients such as nitrogen and phosphorus from the treated water at a high removal rate.
[0003]
[Problems to be solved by the invention]
Conventionally, it is known as a biological nitrification denitrification method that an activated sludge treatment is repeatedly performed in an anaerobic / aerobic state to remove nitrogen as well as organic matter. In addition, it is possible to remove nitrogen and phosphorus simultaneously with the organic matter by repeatedly performing the activated sludge treatment in a completely anaerobic state, an oxygen-free state, and an aerobic state sequentially, as a so-called biological nitrification and denitrification phosphorus removal method. Are known.
However, in these methods, it is difficult to remove nitrogen and phosphorus compounds to such an extent that the final treated water can be effectively reused.
[0004]
Thus, it has been proposed to carry out a final high-order treatment using a reverse osmosis membrane module in order to remove the nitrogen and phosphorus compounds. Because of the large volume of treated water in this treatment, it is appropriate to use a reverse osmosis membrane module having a large permeation flux. As the reverse osmosis membrane module, a crosslinked aromatic polyamide reverse osmosis is used. Attention has been focused on membrane modules.
However, according to the test results of the present inventors, when the final high-order treatment is performed with the crosslinked aromatic polyamide-based reverse osmosis membrane module, the permeation flux decreases relatively early, and I found it difficult to maintain processing speed.
It is presumed that the cause of such a decrease in the early permeation flux is a result of the surfactant contained in the treated water being remarkably adsorbed on the surface of the crosslinked aromatic polyamide membrane and the hydrophilicity of the membrane surface being reduced.
[0005]
An object of the present invention is to treat a sewage in a final high-order sewage treatment under a high and stable permeation flux, and to remove nutrients such as nitrogen and phosphorus at a high removal rate. And to make the treated water usable as hydrophilic water for public facilities.
[0006]
[Means for Solving the Problems]
The method for treating sewage according to the present invention comprises a reverse osmosis membrane module in which the membrane surface in contact with raw water is formed of cellulose acetate and a reverse osmosis module in which the membrane surface in contact with raw water is formed of cross-linked aromatic polyamide. The reverse osmosis membrane module performs a final higher-order treatment in sewage treatment. The reverse osmosis membrane module in the latter stage has a permeation flux of 0.10 m ³ / m ^2.・ [Kgf / cm ² ] · day or more, salt rejection after 30 minutes of operation at 25 ° C. and operating pressure 7.5 kgf / cm ^{2 using} saline having a pH of 6.5 and a concentration of 0.05% as raw water Is preferably 90% or more, and more preferably, a film having an average surface roughness of 55 nm or more.
[0007]
In the present invention, the reason for using a crosslinked aromatic polyamide-based reverse osmosis membrane module in the subsequent reverse osmosis membrane module is that the permeation flux is large and the solute removal rate for nitrogen and phosphorus compounds is large. Because. The cross-linked aromatic polyamide-based film is formed on a porous substrate by a monomer comprising an aromatic polyamine reactant of a monomer having at least two amine functional groups and a polyfunctional acyl halide or a mixture thereof. Prepared by interfacially polymerizing an aromatic amine-reactive reactant (having an average of at least about 2.2 acyl halide groups per molecule of the amine-reactive reactant) in the presence of an amine salt Composite membranes (eg, US Pat. No. 1,948,993) are preferably used, and the aromatic polyamine reactants of monomers having at least two amine functional groups include, for example, m-phenylenediamine, For example, trimesoyl chloride is used as the monomeric aromatic amine reactive reactant comprising an acyl halide.
A reverse osmosis membrane module using a crosslinked aromatic polyamide-based membrane other than this can also be used.
[0008]
In the present invention, the reason for using a reverse osmosis membrane module having a membrane surface formed of cellulose acetate in the former stage is that the decrease in permeation flux due to contact with a surfactant is extremely low, and While ensuring that a sufficient amount of liquid is supplied to the subsequent crosslinked aromatic polyamide-based reverse osmosis membrane module while blocking the reverse osmosis membrane module from the surfactant at the latter stage, thereby achieving a high permeation flux. In order to remove nitrogen and phosphorus at a high removal rate under this condition, the pre-stage reverse osmosis membrane module is entirely made of cellulose acetate and has a thickness of 0.1 to 1 μm on the surface of the sponge layer. In addition to using an asymmetric membrane having a dense skin layer, a composite membrane obtained by casting an ultrathin cellulose acetate thin film on a porous support can also be used. Commercial products of the cellulose acetate reverse osmosis module include reverse osmosis module NTR-1698 manufactured by Nitto Denko, reverse osmosis module SC-3200 manufactured by Toray, and reverse osmosis module manufactured by Fluid System. Module 8221HR and the like.
[0009]
The reverse osmosis membrane module in the latter stage uses a permeation flux of 0.10 m ³ / m ² · [kgf / cm ² ] · day or more in order to secure the above high permeation flux. In addition, in order to secure a high removal rate for nitrogen and phosphorus, a saline solution having a pH of 6.5 and a concentration of 0.05% was used as raw water at 25 ° C. and an operation pressure of 7.5 kgf / cm ² after 30 minutes of operation. The salt rejection of which is 90% or more is used.
In the reverse osmosis membrane module in the latter stage, it is preferable to use a reverse osmosis membrane module having an average surface roughness Ra of 55 nm or more in order to increase the surface area of the membrane and substantially increase the membrane area.
[0010]
The average roughness Ra is defined by the following equation (1), and can be measured by a nuclear power microscope, a friction force microscope, a tunnel microscope, a scanning electron microscope, a transmission electron microscope, or the like.
(Equation 1)

Here, a and b are the lengths of two sides of the designated surface (rectangle), S is the area of the designated surface, f (x, y) is the height within the designated surface, and cellulose acetate o is given by the following equation. It is the average value of the height of the given designated surface.
[0011]
(Equation 2)

[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a sewage treatment facility used in the present invention.
In FIG. 1, reference numeral 1 denotes a coarse filtration device, which is provided with a screen, a sand basin, an oil / fat separation tank, a pH adjusting tank, and the like, for removing coarse suspended matters and fats and oils which are obstacles to a subsequent processing facility. 2 is a biological treatment device. Reference numeral 3 denotes a pretreatment device, which is provided to remove suspended substances and protect the reverse osmosis membrane module provided therefrom from suspended substances. For example, a sand filtration device or a microfiltration device is used. 4 is a raw water tank, 51 is a pre-stage liquid feed pump, 61 is a pre-stage reverse osmosis membrane module in which the membrane surface in contact with raw water is formed of cellulose acetate, 611 is a pre-stage non-permeated water discharge pipe, Numeral 612 indicates the upstream permeated water outflow pipe.
[0013]
In the former cellulose acetate reverse osmosis membrane module, since the cellulose acetate is an ester of cellulose and has a problem of hydrolysis and deterioration due to alkali, the pH of the stock solution is adjusted to about 3 to 7. It is necessary.
In FIG. 1, reference numeral 41 denotes an acid solution tank, and reference numeral 42 denotes a pump for injecting an acid solution into the raw water tank 4. The pump is operated by a pH meter 43, and the pH value in the raw water tank 4 becomes around 5. Adjusted.
[0014]
Reference numeral 7 denotes an intermediate tank, for example, a pipe header; 52, a post-stage liquid feed pump; 62, a post-stage reverse osmosis membrane module in which the membrane surface in contact with raw water is formed of a cross-linked aromatic polyamide; An outflow pipe 620 is a latter-stage non-permeated water pipe. A part of the latter-stage non-permeated water is returned to the raw water tank 4 by a return pipe 620 ′, and the remainder is discharged from the latter-stage non-permeated water discharge pipe 621. Then, the second-stage permeated water is taken out from the second-stage permeated water outflow pipe 622 as service water. Reference numeral 8 denotes an alkaline liquid tank provided as required, and reference numeral 9 denotes a pump for injecting the alkaline liquid into the permeation side of the pre-stage reverse osmosis membrane separation module 61.
[0015]
In order to treat the sewage according to the present invention using the above facility, the sewage is treated by the coarse filtration device 1, the biological treatment device 2, and the pretreatment device 3, and the wastewater is temporarily stored in the raw water tank 4, and is then supplied by the pre-stage liquid supply pump 51. The water is supplied to the pre-stage reverse osmosis membrane separation module 61 at a predetermined pressure, and non-permeated water such as salt is discharged from the pre-stage non-permeated water discharge pipe 611 by preventing the passage of salts and organic substances in the raw water. Permeated water from which salts and the like have been removed at a predetermined removal rate is generated on the side.
In this case, an acid such as sulfuric acid or hydrochloric acid is injected into the raw water tank 4 by the pump 42 to adjust the pH of the raw water to around 5.
[0016]
The pre-stage permeated water of the pre-stage reverse osmosis membrane separation module 61 is temporarily stored in the intermediate tank 7, and if necessary, an alkali solution, for example, sodium hydroxide or potassium hydroxide, is injected by the pump 9 to obtain the permeated water. The pH is adjusted, and this pH-adjusted permeated water is supplied to the latter reverse osmosis membrane separation module 62 at a predetermined pressure by the liquid sending pump 52, and a part of the latter non-permeated water in which the salt is concentrated is sent to the former line At the same time, the remaining non-permeated water is discharged from the latter non-permeated water discharge pipe 621. The second-stage permeated water further desalted by the second-stage reverse osmosis membrane separation module 62 is used as service water such as hydrophilic water.
In the above, all the non-permeated water of the post-stage reverse osmosis membrane separation module 62 can be discharged, and the amount of return to the pre-stage line can be reduced to zero.
[0017]
The second stage liquid feed pump is omitted, and as shown in FIG. 2, the operating pressure of not only the first stage reverse osmosis membrane separation module 61 but also the second stage reverse osmosis membrane separation module 62 is generated by the first stage liquid feed pump 51. In this case, the pre-stage reverse osmosis membrane separation module 61 is also pressurized on its permeation side, so that the permeation side has a pressure resistant structure capable of coping with this pressing force.
In FIG. 2, the same reference numerals as those in FIG. 1 denote the same components. The above-mentioned reverse osmosis membrane separation modules at the front and rear stages include a spiral type, a hollow fiber type, a tuber type, and a frame type. And plate type can be used.
In the above, several module units are connected in series or in parallel to the reverse osmosis membrane separation module, the supply side of these unit groups is connected collectively to the raw water supply pipe, and the permeate side is collectively connected. The one connected to the permeate outlet pipe can also be used.
[0018]
The sewage to be treated by the present invention contains a large amount of a surfactant for draining soap and detergent. Thus, in the case of a reverse osmosis membrane module in which the surface layer of the membrane is formed of cellulose acetate, even if the membrane is in contact with the surfactant, almost no adsorption of the surfactant to the membrane surface is observed, and The bundle is slightly reduced. This surfactant has a relatively high molecular weight and is substantially almost completely blocked by the reverse osmosis membrane module. Therefore, almost complete blocking of the surfactant by the first-stage reverse osmosis membrane module enables low-permeation of the second-stage reverse osmosis membrane module in which the surface layer of the membrane is formed of a cross-linked aromatic polyamide under contact with the surfactant. The reverse reverse osmosis membrane module can effectively exhibit the original high salt removal rate against nitrogen and phosphorus without revealing the fluence, and the nitrogen and phosphorus content is small and the water for hydrophilic use is small. The available high quality permeated water can be obtained.
[0019]
【Example】
〔Example〕
The reverse osmosis membrane module in the first stage had a salt rejection of 98 after 30 minutes of operation at 25 ° C. and an operating pressure of 29.4 kgf / cm ^{2 using} saline having a pH of 6.0 and a concentration of 0.20% as raw water. %, And a spiral reverse osmosis membrane module NTR-1698 manufactured by Nitto Denko Corporation whose membrane is cellulose acetate was used.
[0020]
The reverse osmosis membrane module in the latter stage has a salt rejection of 99 after 30 minutes of operation at 25 ° C. and an operating pressure of 7.5 kgf / cm ^{2 using} saline having a pH of 6.5 and a concentration of 0.05% as raw water. Nitto Denko with a permeation flux of 0.13 m ³ / m ² · [kgf / cm ² ] · day at 0.5%, a cross-linked aromatic polyamide film, and an average surface roughness of 80 nm. A company-made spiral reverse osmosis membrane module was used. The membrane of the reverse osmosis membrane module is composed of a polysulfone porous substrate, m-phenylenediamine of 2.0% by weight, sodium lauryl sulfate of 0.15% by weight, triethylamine of 2.0% by weight, A stock solution containing 4.0% by weight of camphor-sulfonic acid and 20% by weight of isopropyl alcohol was brought into contact with the stock solution thus formed, and a hexane solution containing 0.15% by weight of trimesic acid chloride was brought into contact with the stock solution layer thus formed. Thereafter, it was held for 3 minutes in a hot air dryer at 120 ° C. to form a reaction-produced skin layer having a surface average roughness of 80 nm.
[0021]
In FIG. 1 (alkaline liquid tank 8 and pump 9 are omitted), the raw water having a nitrogen concentration of 50 ppm, an ammonia nitrogen concentration of 50 ppm, a phosphorus concentration of 50 ppm, a detergent in a high concentration, and a pH value adjusted to 6 is used. It is stored in the raw water tank 4, and the initial pressure of the first-stage liquid pump 51 is set to 30 kgf / cm ² , and the second-stage liquid pump 52 is set to 7.5 kgf / cm ² , and the initial permeation of the reverse osmosis membrane module 62 is performed. The operation was performed such that the flux was 0.13 m ³ / m ² · [kgf / cm ² ] · day, and the operation was continued for 200 hours.
The quality of the permeated water of the latter reverse osmosis membrane module 62 is as shown in Table 1, and the state of the permeated water flow rate decreasing over time is as shown in FIG.
[0022]
[Comparative Example 1]
Only the spiral reverse osmosis membrane module manufactured by Nitto Denko Corporation used as the pre-stage reverse osmosis membrane module in the example was operated at an operating pressure of 30 kgf / cm ² to treat the same adjusted raw water as in the example. The initial permeation flux was 0.033 m ³ / m ² · [kgf / cm ² ] · day.
The water quality of the permeated water in this comparative example is as shown in Table 1, and the state of the permeate flow rate decreasing with time is as shown in FIG.
[0023]
[Comparative Example 2]
Only the spiral reverse osmosis membrane module manufactured by Nitto Denko Corporation, which was used as the post-stage reverse osmosis membrane module in the examples, was operated at an operating pressure of 10 kgf / cm ² to treat the same adjusted raw water as in the examples. The initial permeation flux was 0.08 m ³ / m ² · [kgf / cm ² ] · day. The water quality of the permeated water in this comparative example is as shown in Table 1, and the state of the permeate flow rate decreasing with time is as shown in FIG.
[0024]
[Table 1]

[0025]
As is clear from Table 1, according to the method for treating sewage according to the present invention, even if the sewage contains a large amount of a surfactant, nitrogen and phosphorus compounds can be treated in extremely small amounts, and the permeation thereof can be improved. Since the flux can be made sufficiently large, the treated water can be effectively used as service water.
[0026]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the sewage treatment method of this invention, a surfactant is substantially shut off, and the original excellent removal rate and nitrogen flux of the crosslinked aromatic polyamide-based reverse osmosis membrane module for nitrogen and phosphorus compounds are improved. Even if the sewage contains a large amount of surfactant, it can be treated with extremely small amounts of nitrogen and phosphorus, and its permeation flux can be sufficiently increased. And can be used effectively by returning it to a water source.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of a sewage treatment facility used in the present invention.
FIG. 2 is an explanatory diagram showing another example of a sewage treatment facility used in the present invention.
FIG. 3 is a table showing the permeation flux characteristics over time of an example according to the present invention and a comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rough filtration apparatus 2 Biological treatment apparatus 3 Pretreatment apparatus 4 Raw water tank 51 Front liquid feed pump 52 Rear liquid feed pump 61 Front reverse osmosis membrane module 62 Rear reverse osmosis membrane module 7 Intermediate tank

Claims (3)

Sewage treatment by a reverse osmosis membrane module in which the membrane surface in contact with raw water is formed of cellulose acetate and a reverse osmosis membrane module in which the membrane surface in contact with raw water is formed of cross-linked aromatic polyamide Sewage treatment method, wherein a final higher-order treatment is performed. The permeation flux of the latter reverse osmosis membrane module is not less than 0.10 m ³ / m ² · [kgf / cm ² ] · day, and the temperature is 25 ° C. using a saline solution having a pH of 6.5 and a concentration of 0.05% as a raw water. , operating pressure 7.5 kgf / salt rejection of at cm ² at 30 minutes after the operation is 90% or more claims 1 processing method sewage according. The method for treating sewage according to claim 1 or 2, wherein the average surface roughness of the membrane surface of the reverse osmosis membrane module is 55 nm or more.

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