JP2006122908A - Pure water producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce pure water of high quality by suppressing pH variation of inlet water of an RO membrane separation apparatus, and stably keeping pH conditions suitable to RO treatment, in a pure water producing method wherein acid is added to water to be treated, deaerated, and made to pass through the RO membrane separation apparatuses serially arranged in multiple stages. <P>SOLUTION: Water subjected to deaeration 2 is brought into contact with activated carbon 3, and the water after contacting activated carbon is made to pass through the RO membrane separation apparatuses 4-6 serially arranged in multiple stages. By the present invention, deaerated water is treated with activated carbon to stabilize pH, and feed water of the multi-stage RO treatment is easily adjusted to the optimum pH conditions, to stably produce pure water of high purity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は純水の製造方法に係り、特に、被処理水に酸を添加して脱気処理した後、多段に直列配置した逆浸透（ＲＯ）膜分離装置に順次通水して純水を製造する方法において、ＲＯ膜分離装置の入口水のｐＨ変動を抑え、ＲＯ膜分離処理に好適なｐＨ条件を安定に維持することにより、高水質の純水を製造する方法に関する。   The present invention relates to a method for producing pure water, and in particular, after adding an acid to the water to be treated and deaeration treatment, the water is successively passed through reverse osmosis (RO) membrane separation devices arranged in series in multiple stages. The present invention relates to a method for producing high-quality pure water by suppressing pH fluctuation of inlet water of an RO membrane separation apparatus and stably maintaining pH conditions suitable for RO membrane separation treatment.

従来、市水、井水、工水、回収水、その他の水から純水（一次純水）を製造する方法として、これらの水を必要に応じて前処理（除濁、除塩素）した後、酸を添加して脱炭酸処理し、脱炭酸処理水を２段に直列配置したＲＯ膜分離装置に順次通水処理（２段ＲＯ処理）する方法がある。   Conventionally, as a method of producing pure water (primary pure water) from city water, well water, industrial water, recovered water, and other water, after pre-treatment (turbidity removal, chlorine removal) of these waters as needed There is a method in which an acid is added for decarboxylation treatment, and the decarboxylation treatment water is sequentially passed through a RO membrane separation device in which decarboxylation treatment water is arranged in two stages (two-stage RO treatment).

また、このような２段ＲＯ処理において、処理水質の改善を図るために、ＲＯ膜分離装置の給水に水酸化ナトリウム（ＮａＯＨ）等のアルカリを注入し、ＲＯ膜分離装置に供給される水中に残留する炭酸（ＣＯ₂）をイオン化（ＨＣＯ₃ ^-，ＣＯ₃ ^2-）してＲＯ処理する方法が提案されている。 Further, in such a two-stage RO treatment, in order to improve the quality of the treated water, an alkali such as sodium hydroxide (NaOH) is injected into the feed water of the RO membrane separation device and the water supplied to the RO membrane separation device is injected. A method has been proposed in which residual carbonic acid (CO ₂ ) is ionized (HCO ₃ ⁻ , CO ₃ ²⁻ ) and subjected to RO treatment.

例えば、特公平６−４９１９１号公報には、原水に酸を添加した後、脱炭酸塔で脱炭酸処理し、脱炭酸処理水にアルカリを添加した後、２段ＲＯ処理する方法が記載され、また、特公平８−２９３１５号公報には、原水に酸を添加した後、脱気装置で脱炭酸処理し、脱気処理水にアルカリを添加した後、２段ＲＯ処理する方法が記載されている。   For example, Japanese Patent Publication No. 6-49191 describes a method in which an acid is added to raw water, then decarboxylated in a decarboxylation tower, an alkali is added to decarbonated water, and then a two-stage RO treatment is performed. Japanese Patent Publication No. 8-29315 describes a method of performing a two-stage RO treatment after adding an acid to raw water, followed by decarboxylation with a degassing device, adding alkali to the degassed water. Yes.

なお、このようにして得られる２段ＲＯ処理水は、必要に応じてイオン交換処理を施して、更に純度を高める。   In addition, the two-stage RO treated water obtained in this way is subjected to ion exchange treatment as necessary to further increase the purity.

また、水の純度をより一層高めるために３段に直列配置したＲＯ膜分離装置に順次通水処理（３段ＲＯ処理）する方法も公知であり、例えば、特開平５−２２０４７９号公報には、第１段目のＲＯ膜として負荷電膜を用い、第１段目のＲＯ処理水（第１段目のＲＯ膜分離装置の透過水）にアルカリを添加した後、第２段目のＲＯ膜分離装置及び第３段目のＲＯ膜分離装置に順次通水し、第２，３段目のＲＯ膜分離装置の濃縮水を前段のＲＯ膜分離装置に返送する方法が記載されている。更に、特開平７−１６５６５号公報には、３段ＲＯ処理において、２段目のＲＯ膜分離装置の濃縮水のｐＨに基いて２段目のＲＯ膜分離装置の給水にアルカリを添加する方法が記載されている。   Further, in order to further increase the purity of water, there is also known a method of sequentially passing water through a RO membrane separator arranged in three stages (three-stage RO treatment). For example, JP-A-5-220479 discloses After using a negatively charged membrane as the first-stage RO membrane and adding alkali to the first-stage RO treated water (permeated water of the first-stage RO membrane separation device), the second-stage RO A method is described in which water is sequentially passed through a membrane separator and a third-stage RO membrane separator, and the concentrated water of the second and third-stage RO membrane separators is returned to the preceding RO membrane separator. Furthermore, Japanese Patent Laid-Open No. 7-16565 discloses a method of adding alkali to the feed water of the second-stage RO membrane separator based on the pH of the concentrated water of the second-stage RO membrane separator in the three-stage RO treatment. Is described.

なお、従来、超純水製造工程において、活性炭処理を採用する場合があるが、従来の活性炭処理工程は、ＴＯＣの吸着除去や塩素の除去を目的とするものであり、脱炭酸処理後のＲＯ膜分離装置への給水のｐＨ調整を目的としたものはない。
特公平６−４９１９１号公報 特公平８−２９３１５号公報 特開平５−２２０４７９号公報 特開平７−１６５６５号公報 Conventionally, activated carbon treatment may be employed in the ultrapure water production process, but the conventional activated carbon treatment process is intended for TOC adsorption removal and chlorine removal. None is intended to adjust the pH of the feed water to the membrane separator.
Japanese Patent Publication No. 6-49191 Japanese Patent Publication No. 8-29315 Japanese Patent Laid-Open No. 5-220479 JP 7-16565 A

上記従来の方法のうち、特公平６−４９１９１号公報及び同８−２９３１５号公報に開示される方法では、酸添加後の水のｐＨ幅を小さく押えても、脱炭酸処理後のｐＨは酸添加後のｐＨ幅の５倍以上の変動を示す。   Among the conventional methods described above, in the methods disclosed in Japanese Patent Publication Nos. 6-49191 and 8-29315, the pH after decarboxylation is acid even if the pH range of water after acid addition is kept small. It shows a fluctuation more than 5 times the pH range after the addition.

例えば、図２は、水に硫酸（Ｈ₂ＳＯ₄）を添加した後、膜脱気装置で脱気処理した場合の膜脱気装置入口水（酸添加後の水）のｐＨ変動と膜脱気装置出口水（脱気処理後の水）のｐＨ変動を示すグラフであるが、膜脱気装置入口水のｐＨを４．８〜４．９の範囲に抑えても、膜脱気装置出口水のｐＨは５．３〜５．８と大きく変動していることがわかる。 For example, FIG. 2, after the addition of sulfuric acid (H ₂ SO ₄₎ in water, pH change and Makuda' membrane degasifier inlet water in the case of degassing treatment with membrane degasser (water after acid addition) Although it is a graph which shows the pH fluctuation | variation of air apparatus exit water (water after deaeration process), even if it suppresses pH of the film deaerator inlet water to the range of 4.8-4.9, it is a film | membrane deaerator exit It can be seen that the pH of water varies greatly from 5.3 to 5.8.

このように酸添加後のｐＨ幅が±０．０５であっても、脱気処理後のｐＨ幅は±０．２５にもなるのは、膜脱気装置の入口水のｐＨ条件のわずかな変化により、脱気膜におけるＣＯ₂除去性能が異なるものとなり、脱気処理後のｐＨが大きく変動することによる。 Thus, even if the pH range after the acid addition is ± 0.05, the pH range after the deaeration treatment is ± 0.25. This is because the CO ₂ removal performance in the degassing membrane varies depending on the change, and the pH after degassing treatment varies greatly.

以上のように、酸添加後脱炭酸処理する方法では、脱炭酸処理水のｐＨ幅が大きいことから、ＲＯ処理に際してアルカリを添加した場合、ｐＨ幅を例えば±０．０５というように小さくすることは極めて困難であり、ＲＯ膜分離装置の給水はｐＨ変動の大きいものとなる。   As described above, in the method of decarboxylation after the addition of acid, the pH range of decarboxylated water is large. Therefore, when alkali is added during RO treatment, the pH range should be reduced to, for example, ± 0.05. Is extremely difficult, and the water supply of the RO membrane separation device has a large pH fluctuation.

特に、特開平５−２２０４７９号公報に記載される３段ＲＯ処理のように、後段のＲＯ処理の濃縮水を前段のＲＯ膜分離装置に返送する方法を採用した場合には、当該ＲＯ膜分離装置の入口水のｐＨを一定に制御することは極めて困難なものとなる。なお、この方法のように、低圧の後段のＲＯ処理の濃縮水を高圧の前段のＲＯ膜分離装置に戻すためには、更に、この返送のためのブースターポンプ等の高圧ポンプが必要となり、コスト高騰につながる。   In particular, when a method of returning the concentrated water from the subsequent RO treatment to the preceding RO membrane separation device, such as the three-stage RO treatment described in JP-A-5-220479, the RO membrane separation is performed. It becomes extremely difficult to control the pH of the inlet water of the apparatus to be constant. In addition, in order to return the concentrated low-pressure RO treatment water to the high-pressure pre-stage RO membrane separator as in this method, a high-pressure pump such as a booster pump is required for this return, and the cost It leads to soaring.

また、特開平７−１６５６５号公報に記載されるように、ＲＯ膜分離装置の濃縮水のｐＨに基いてアルカリ添加量を制御する方法では、ＲＯ膜分離装置における滞留時間に相当する時間のタイムラグが生じる。このため、水質変動に対応してｐＨを制御することが難しい。   In addition, as described in JP-A-7-16565, in the method of controlling the amount of alkali added based on the pH of the concentrated water in the RO membrane separator, a time lag corresponding to the residence time in the RO membrane separator Occurs. For this reason, it is difficult to control pH in response to water quality fluctuations.

ところで、ＲＯ膜分離装置による処理においては、その給水の水質に応じて最適なｐＨ条件が存在し、高水質のＲＯ処理水を得るためには、ＲＯ膜分離装置の給水をその最適ｐＨ条件に調整する必要がある。   By the way, in the treatment by the RO membrane separation device, there is an optimum pH condition depending on the quality of the feed water, and in order to obtain high quality RO treated water, the feed water of the RO membrane separation device is set to the optimum pH condition. It needs to be adjusted.

しかしながら、従来においては、上述の如く、ＲＯ膜分離装置の給水のｐＨを最適ｐＨ条件に調整することが難しく、このため、良好な水質の処理水を安定に得ることができなかった。   However, in the past, as described above, it is difficult to adjust the pH of the feed water of the RO membrane separation device to the optimum pH condition, and therefore, treated water with good water quality could not be obtained stably.

本発明は上記従来の問題点を解決し、被処理水に酸を添加して脱気処理した後、３段に直列配置したＲＯ膜分離装置に順次通水して純水を製造する方法において、ＲＯ膜分離装置の入口水のｐＨ変動を抑え、ＲＯ処理に好適なｐＨ条件を安定に維持することにより、高水質の純水を製造する方法を提供することを目的とする。 The present invention solves the above-mentioned conventional problems, and in a method for producing pure water by adding water to the water to be treated and degassing it, and then sequentially passing water through an RO membrane separator arranged in series in three stages. An object of the present invention is to provide a method for producing high-quality pure water by suppressing the pH fluctuation of the inlet water of the RO membrane separation apparatus and stably maintaining pH conditions suitable for the RO treatment.

本発明の純水の製造方法は、被処理水に酸を添加して脱気処理した後、３段に直列配置した逆浸透膜分離装置に順次通水して純水を製造する方法において、３段目の逆浸透膜分離装置の逆浸透膜が正荷電膜であり、脱気処理後の水を活性炭と接触させ、該活性炭接触後の水を３段に直列配置した前記逆浸透膜分離装置に順次通水することを特徴とする。 The method for producing pure water of the present invention is a method for producing pure water by adding water to the water to be treated and degassing it, and then sequentially passing water through a reverse osmosis membrane separation device arranged in series in three stages. The reverse osmosis membrane separation wherein the reverse osmosis membrane of the third stage reverse osmosis membrane separation device is a positively charged membrane, the water after deaeration treatment is brought into contact with activated carbon, and the water after contact with the activated carbon is arranged in three stages in series It is characterized by sequentially passing water through the device.

脱気処理水を活性炭で処理して得られる水のｐＨは、脱気処理水より若干高く、小さいｐＨ幅で安定している。この活性炭処理水のｐＨ幅が小さく安定するのは、活性炭処理における撹拌、滞留、加圧効果等の物理的作用によるものが主であり、一部にイオンの吸脱着による化学的安定作用があると考えられる。また、活性炭処理水のｐＨが脱気処理水のｐＨより高いのは、活性炭には、炭酸（ＣＯ₂）をイオン化（ＨＣＯ₃ ^-，ＣＯ₃ ^2-）する触媒的な化学作用があるためと考えられる。このような物理、化学的なｐＨ安定化作用は、本発明に係る研究によってはじめて明らかになったものである。活性炭のほかに濾過砂のようなものを用いても物理的作用は期待できるが、上記のような化学的作用は期待できないため、ｐＨ安定効果は落ちるものである。 The pH of water obtained by treating the degassed water with activated carbon is slightly higher than that of the degassed water and is stable at a small pH range. The pH range of this activated carbon treated water is small and stable mainly due to physical action such as stirring, retention, pressurizing effect, etc. in activated carbon treatment, and partly has chemical stabilization action due to adsorption / desorption of ions. it is conceivable that. The activated carbon treated water has a higher pH than the degassed treated water because activated carbon has a catalytic chemical action to ionize (HCO ₃ ⁻ , CO ₃ ²⁻ ) carbonic acid (CO ₂ ). Conceivable. Such physical and chemical pH stabilizing action has been clarified for the first time by the research according to the present invention. A physical action can be expected even when using something like filter sand in addition to activated carbon, but since the chemical action as described above cannot be expected, the pH stabilizing effect is lowered.

本発明では、このように脱気処理水を活性炭処理することでｐＨを安定させ、３段ＲＯ処理の給水を容易に最適ｐＨ条件に調整することにより、高純度の純水を安定に製造する。 In the present invention, the degassed treated water is treated with activated carbon in this way to stabilize the pH, and the water in the three- stage RO treatment is easily adjusted to the optimum pH condition to stably produce high-purity pure water. .

本発明の純水の製造方法によれば、被処理水に酸を添加して脱気処理した後、３段に直列配置したＲＯ膜分離装置に順次通水して純水を製造する方法において、ＲＯ膜分離装置の入口水のｐＨ変動を抑え、ＲＯ処理に好適なｐＨ条件を安定に維持することにより、高水質の純水を製造することができる。 According to the method for producing pure water of the present invention, in the method for producing pure water by adding water to the water to be treated and performing deaeration treatment, then sequentially passing the water through RO membrane separation devices arranged in series in three stages. By suppressing the pH fluctuation of the inlet water of the RO membrane separation apparatus and stably maintaining pH conditions suitable for the RO treatment, high-quality pure water can be produced.

以下に、図面を参照して本発明の実施の形態を説明する。   Embodiments of the present invention will be described below with reference to the drawings.

図１は本発明の純水の製造方法の実施の形態を示す系統図である。   FIG. 1 is a system diagram showing an embodiment of a method for producing pure water according to the present invention.

図示の方法は、脱気処理水を３段に直列配置したＲＯ膜分離装置に順次通水して純水を製造するものであり、まず、市水、工水、井水、回収水（半導体製造工程等排出される使用済超純水）等に必要に応じて凝集沈殿、浮上、濾過、活性炭吸着などの前処理を施して得られる原水を、原水タンク１からポンプＰ−１で抜き出し、酸を添加した後、脱気装置２で脱気処理する。なお、ここで添加される酸としては硫酸（Ｈ₂ＳＯ₄）、塩酸（ＨＣｌ）等が好適であり、その添加量は原水中の炭酸イオン、重炭酸イオンを炭酸の形態に変換するようなｐＨとなるような量であり、処理温度にもよるが、通常、脱気装置２に導入される水のｐＨが５以下、好ましくは５〜４以下、より好ましくは５〜４．５となる量とするのが好ましい。ｐＨ４より低くすると、後述するようにＲＯ処理に好適なｐＨに調整するアルカリ剤が多くなり、好ましくない。従って、酸添加後、撹拌機Ｍ−１で十分に混合均一化した水のｐＨをｐＨ計Ｈ−１で計測し、このｐＨ計Ｈ−１に連動する薬注ポンプＰ−２により、上記ｐＨ範囲となるように酸添加量を制御する。制御方法としては、比例制御、またはＰＩＤ制御などのコントローラにより制御する。 In the method shown in the figure, pure water is produced by sequentially passing degassed treated water through RO membrane separation devices arranged in series in three stages. First, city water, industrial water, well water, recovered water (semiconductors) The raw water obtained by performing pretreatment such as coagulation sedimentation, flotation, filtration, activated carbon adsorption, etc., if necessary, is extracted from the raw water tank 1 with the pump P-1 After the acid is added, the deaeration process is performed by the deaerator 2. The acid added here is preferably sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl), etc., and the amount added is such that carbonate ions and bicarbonate ions in the raw water are converted into a carbonate form. The amount is such that the pH is reached, and depending on the treatment temperature, the pH of the water introduced into the deaerator 2 is usually 5 or less, preferably 5 to 4 or less, more preferably 5 to 4.5. An amount is preferred. If it is lower than pH 4, as will be described later, the amount of alkaline agent adjusted to a pH suitable for RO treatment increases, which is not preferable. Therefore, after the acid addition, the pH of water sufficiently mixed and homogenized by the stirrer M-1 is measured by the pH meter H-1, and the above pH is adjusted by the chemical injection pump P-2 linked to the pH meter H-1. The acid addition amount is controlled so as to be within the range. As a control method, control is performed by a controller such as proportional control or PID control.

脱気装置２としては、気体分離膜の一方の側に給水し、他方の透過側を減圧して水中のガス成分を除去する膜脱気装置、気液接触充填材に散水し、ガスを真空ポンプで吸引する真空脱気装置等を使用することができる。脱気装置２では、原水中の炭酸が炭酸ガスとして水から分離、除去される。脱気（脱炭酸）された水のｐＨは、多少上昇する。この上昇度は脱炭酸量に関係し、脱炭酸量の変化により脱気装置２からの流出水のｐＨは変動する。なお、この脱気処理により、水中の溶存酸素も除去される。   As the deaeration device 2, water is supplied to one side of the gas separation membrane, the other permeate side is depressurized to remove gas components in water, water is sprayed onto the gas-liquid contact filler, and the gas is vacuumed A vacuum deaerator or the like that sucks with a pump can be used. In the deaeration device 2, carbon dioxide in the raw water is separated and removed from the water as carbon dioxide gas. The pH of degassed (decarboxylated) water rises somewhat. This degree of increase is related to the amount of decarboxylation, and the pH of the effluent from the degassing device 2 varies depending on the change in the amount of decarboxylation. In addition, dissolved oxygen in water is also removed by this deaeration treatment.

脱気装置２の流出水は次いで活性炭塔３に通水される。この活性炭塔３としては、粒状活性炭の充填層を形成したものを使用し、下降流又は上向流で通水する。通水条件には特に制限はないが、通水流速としてはＳＶ＝１０〜３０ｈｒ^-1が適当である。 The effluent from the deaerator 2 is then passed through the activated carbon tower 3. As this activated carbon tower 3, what formed the packed bed of granular activated carbon is used, and it water-flows by a downward flow or an upward flow. Although there is no restriction | limiting in particular in water flow conditions, SV = 10-30hr < ^-1 > is suitable as a water flow rate.

一般に、活性炭の充填層内には、微生物等が繁殖して目詰りし、１週間〜数カ月程度で逆洗したり、活性炭を取り替えたりする必要があるが、本発明では脱気処理により微生物の増殖に必要な溶存酸素が除去された水が導入されるため、活性炭塔内の微生物繁殖の問題がなく、目詰り等のトラブルも殆どない。このため、活性炭の取り替えの必要はなく、また、逆洗頻度も著しく少なくて足り、年に数回の逆洗で十分な機能を得ることができる。   In general, microorganisms and the like propagate and clog in the packed bed of activated carbon, and it is necessary to backwash or replace the activated carbon in about a week to several months. Since water from which dissolved oxygen necessary for growth is removed is introduced, there is no problem of microbial propagation in the activated carbon tower, and there is almost no trouble such as clogging. For this reason, it is not necessary to replace the activated carbon, and the frequency of backwashing is remarkably low, and a sufficient function can be obtained by backwashing several times a year.

この活性炭塔３に通水することにより得られる活性炭処理水のｐＨは、脱気処理水のｐＨよりも若干高い値で、極めて小さい変動幅で安定する。   The pH of the activated carbon treated water obtained by passing through the activated carbon tower 3 is slightly higher than the pH of the degassed treated water, and is stable with a very small fluctuation range.

例えば、脱気装置２の入口水のｐＨが４．８〜４．９の場合、前述の如く、脱気装置２の出口水のｐＨは脱気処理の程度の差により、ｐＨ５．３〜５．８と大きく変動するが、これを活性炭塔３に通水して得られる活性炭塔３の出口水はｐＨ６．０〜６．１程度と、ｐＨ変動幅は極めて小さく、ｐＨ値が安定する。   For example, when the pH of the inlet water of the degassing device 2 is 4.8 to 4.9, the pH of the outlet water of the degassing device 2 is pH 5.3 to 5 depending on the degree of the degassing treatment as described above. However, the outlet water of the activated carbon tower 3 obtained by passing the water through the activated carbon tower 3 has an extremely small pH fluctuation range of about 6.0 to 6.1, and the pH value is stable.

活性炭塔３の流出水は、必要により酸又はアルカリを添加してＲＯ処理に好適なｐＨ値に調整した後、第１段目のＲＯ膜分離装置（以下「第１ＲＯ装置」と称す。）４、第２段目のＲＯ膜分離装置（以下「第２ＲＯ装置」と称す。）５、第３段目のＲＯ膜分離装置（以下「第３ＲＯ装置」と称す。）６に順次通水して純水を得る。   The effluent of the activated carbon tower 3 is adjusted to a pH value suitable for RO treatment by adding acid or alkali as necessary, and then the first stage RO membrane separation device (hereinafter referred to as “first RO device”) 4. Then, water is sequentially passed through the second stage RO membrane separation apparatus (hereinafter referred to as “second RO apparatus”) 5 and the third stage RO membrane separation apparatus (hereinafter referred to as “third RO apparatus”) 6. Get pure water.

ところで、ＲＯ処理に当り、ＲＯ処理の給水のｐＨは得られる処理水（透過水）の水質に大きく影響し、ＲＯ処理に好適なｐＨ値が存在する。また、この好適なｐＨ値は原水水質（主に全炭酸濃度）によって異なる。   By the way, in the RO treatment, the pH of the feed water of the RO treatment greatly affects the quality of the treated water (permeated water) to be obtained, and there is a pH value suitable for the RO treatment. Moreover, this suitable pH value changes with raw | natural water quality (mainly total carbonic acid concentration).

例えば、図３，４は、３段ＲＯ処理の給水と得られる処理水（第３ＲＯ装置の透過水）の比抵抗との関係を示すグラフであり、図３は全炭酸濃度が１４ｐｐｍの原水（水道水単独）を脱気処理した後３段ＲＯ処理する場合を示し、図４は全炭酸濃度が４．３ｐｐｍの原水（水道水：回収水＝３：７）を脱気処理した後３段ＲＯ処理する場合を示すものであるが、これらのグラフから、３段ＲＯ処理の給水のｐＨは、原水の全炭酸濃度が１４ｐｐｍの場合はｐＨ７．１程度が好ましく、原水の全炭酸濃度が４．３ｐｐｍの場合は、ｐＨ６．０〜６．１程度が好ましいことがわかる。このように、原水の全炭酸濃度に応じて、ＲＯ処理の最適ｐＨ値が異なるものとなり、全炭酸濃度が高い程最適ｐＨ値が高くなるが、これは、原水の全炭酸濃度に対応して脱気処理後の全炭酸濃度も高くなり、その分、炭酸のイオン化に必要なアルカリ量が増えるためである。アルカリ添加量を最適ｐＨ値より多くすると逆にアルカリ負荷が大となり生産水比抵抗は低下してくるため、最適ｐＨ範囲が存在する。   For example, FIGS. 3 and 4 are graphs showing the relationship between the water supply of the three-stage RO treatment and the specific resistance of the obtained treated water (permeated water of the third RO device), and FIG. 3 is a raw water having a total carbonic acid concentration of 14 ppm ( Figure 3 shows the case where the three-stage RO treatment is performed after degassing the tap water alone, and Fig. 4 shows the third stage after degassing the raw water (tap water: recovered water = 3: 7) having a total carbonic acid concentration of 4.3 ppm. Although the case where RO treatment is shown is shown, from these graphs, the pH of the feed water of the three-stage RO treatment is preferably about pH 7.1 when the total carbonate concentration of the raw water is 14 ppm, and the total carbonate concentration of the raw water is 4 In the case of .3 ppm, it is understood that pH of about 6.0 to 6.1 is preferable. Thus, the optimum pH value for RO treatment differs depending on the total carbonic acid concentration of the raw water. The higher the total carbonic acid concentration, the higher the optimum pH value. This corresponds to the total carbonic acid concentration of the raw water. This is because the total carbonic acid concentration after the deaeration treatment also increases, and the amount of alkali necessary for ionization of carbonic acid increases accordingly. On the contrary, when the amount of alkali added is larger than the optimum pH value, the alkali load becomes large and the specific resistance of the produced water is lowered, so that an optimum pH range exists.

このようなことから、ＲＯ処理の給水は、その原水の水質に応じて最適ｐＨ値に調整する必要がある。この場合、最適ｐＨは原水の水質により、一概に特定できないので、装置運転開始に先立ち、最終処理水（純水）に要求される純度とＲＯ処理の給水のｐＨとの関係を、給水ｐＨを変化させることにより確認し、最適ｐＨ値を予め設定しておくのが好ましい。   For this reason, it is necessary to adjust the RO water supply to an optimum pH value according to the quality of the raw water. In this case, since the optimum pH cannot be specified unconditionally due to the quality of the raw water, the relationship between the purity required for the final treated water (pure water) and the pH of the RO treatment feed water is determined before It is preferable that the optimum pH value is set in advance by confirming the change.

このＲＯ処理の給水のｐＨ調整は、狭いｐＨ範囲で制御できる程、得られる処理水の純度が高いものとなるが、本発明では、活性炭処理によりｐＨ値が安定した水をＲＯ処理の給水とするため、ｐＨ調整により狭いｐＨ範囲に容易に制御することができる。   In this RO treatment, the pH of the feed water is adjusted so that it can be controlled within a narrow pH range, and the purity of the obtained treated water is high. Therefore, it can be easily controlled to a narrow pH range by adjusting the pH.

前述の如く、脱気処理水を活性炭処理して得られる水のｐＨは約６．０〜６．１であるため、図４に示す如く、原水の全炭酸濃度が４．３ｐｐｍの場合には特にｐＨ調整することなくＲＯ処理することができる。   As described above, since the pH of the water obtained by treating the degassed water with activated carbon is about 6.0 to 6.1, as shown in FIG. 4, when the total carbonic acid concentration of the raw water is 4.3 ppm, In particular, RO treatment can be performed without adjusting pH.

また、図３に示す如く、原水の全炭酸濃度が比較的多い場合には、一般にアルカリを添加してｐＨを高める必要があり、逆に原水の全炭酸濃度が比較的少ない場合には、一般に酸を添加してｐＨを下げる必要がある。   In addition, as shown in FIG. 3, when the total carbonic acid concentration of the raw water is relatively high, it is generally necessary to increase the pH by adding an alkali. Conversely, when the total carbonic acid concentration of the raw water is relatively low, It is necessary to add an acid to lower the pH.

ここで、アルカリとしては、水酸化ナトリウム（ＮａＯＨ）等を用いることができ、また、酸としては、ＨＣｌ，Ｈ₂ＳＯ₄等を用いることができる。 Here, sodium hydroxide (NaOH) or the like can be used as the alkali, and HCl, H ₂ SO ₄ or the like can be used as the acid.

図１においては、活性炭塔３の流出水に必要に応じて酸又はアルカリを添加後、撹拌機Ｍ−２で十分に混合均一化した水のｐＨをｐＨ計Ｈ−２で計測し、このｐＨ計Ｈ−１に連動するポンプＰ−３，Ｐ−４により、好適ｐＨ値となるように制御する。   In FIG. 1, after adding acid or alkali to the effluent of the activated carbon tower 3 as necessary, the pH of the water sufficiently mixed and homogenized with the stirrer M-2 is measured with a pH meter H-2. It controls so that it may become a suitable pH value with the pumps P-3 and P-4 interlock | cooperated with the total H-1.

ｐＨ調整後の水は、高圧ポンプＰ−５で加圧して第１ＲＯ装置４に供給する。この第１ＲＯ装置４の給水圧力は、原水の塩類濃度にもよるが、通常の場合、５〜７．５ｋｇ／ｃｍ²とすると、原水中の塩類，ＴＯＣの殆どを排除することができる。この第１ＲＯ装置４の濃縮水は系外へ排出し、透過水は、第１ＲＯ装置４に給水される活性炭塔３の流出水と同様に、ｐＨ計Ｈ−３とこれに連動するポンプＰ−６，Ｐ−７により必要に応じて酸又はアルカリを添加した後撹拌機Ｍ−３で混合し、再度ｐＨ調整した後、第２ＲＯ装置５に供給する。第２ＲＯ装置５では第２ＲＯ装置４の透過水中に微量残留する塩類が除去され、一次純水となる。特に、この第２ＲＯ装置５では残留アニオンを効果的に除去でき、アニオンは殆ど残らない。 The water after pH adjustment is pressurized by the high-pressure pump P-5 and supplied to the first RO device 4. Although the feed water pressure of the first RO device 4 depends on the salt concentration of the raw water, in the normal case, when it is 5 to 7.5 kg / cm ² , most of the salts and TOC in the raw water can be eliminated. The concentrated water of the first RO device 4 is discharged out of the system, and the permeated water is the pH meter H-3 and the pump P- linked to this in the same manner as the outflow water of the activated carbon tower 3 fed to the first RO device 4. After adding acid or alkali as needed with 6, P-7, it mixes with stirrer M-3, pH is adjusted again, and it supplies to the 2nd RO apparatus 5. FIG. The second RO device 5 removes traces of salts remaining in the permeated water of the second RO device 4 to form primary pure water. In particular, the second RO device 5 can effectively remove residual anions, and hardly leaves anions.

第２ＲＯ装置５の透過水は更に第３ＲＯ装置６に供給し、極微量残留するイオンが除去された透過水を、高純度の一次純水として取り出す。   The permeated water of the second RO device 5 is further supplied to the third RO device 6, and the permeated water from which extremely small amounts of remaining ions have been removed is taken out as high purity primary pure water.

この一次純水は、イオン交換装置又は、サブシステム（二次純水装置）に送られ、更に高度処理され、得られた超純水は、半導体製造工程や医薬品製造工程等に供給される。   This primary pure water is sent to an ion exchange device or a subsystem (secondary pure water device), and further subjected to advanced treatment, and the obtained ultrapure water is supplied to a semiconductor manufacturing process, a pharmaceutical manufacturing process, and the like.

一方、第２ＲＯ装置５及び第３ＲＯ装置６の濃縮水は、第１ＲＯ装置４でＲＯ処理された透過水から得られる比較的良好な水質の水であるため、水回収率の向上の面から、これを前段工程に戻して再処理する。この場合、この濃縮水をＲＯ処理のｐＨ調整後の工程に戻すとｐＨ変動の恐れがあり、また、高圧ポンプＲ５の下流側に戻すには、前述の如く、別途ポンプを必要とするため、この高圧ポンプ及びｐＨ調整位置よりも前段に戻すのが好ましい。濃縮水の好適な返送先としては、酸添加前の原水ラインや活性炭塔３の前後が考えられるが、特に、図示の如く、活性炭塔３の入口側に返送するのが好ましい。即ち、原水ラインに返送した場合には、脱気装置２の被処理水が増え不経済である。活性炭塔３の出口側に返送した場合にはこのような問題はないが、活性炭塔３の入口側に返送し、活性炭処理することにより、活性炭処理によるｐＨ安定化作用でｐＨ変動幅が小さく抑えられ、極めて有利である。   On the other hand, the concentrated water of the second RO device 5 and the third RO device 6 is water of relatively good quality obtained from the permeated water that has been RO-treated by the first RO device 4, and therefore, from the aspect of improving the water recovery rate, This is returned to the previous step and reprocessed. In this case, if this concentrated water is returned to the step after the pH adjustment of the RO treatment, there is a risk of pH fluctuation, and in order to return to the downstream side of the high pressure pump R5, a separate pump is required as described above. It is preferable to return to the previous stage from this high-pressure pump and the pH adjustment position. As a suitable return destination of the concentrated water, the raw water line before the acid addition and the front and back of the activated carbon tower 3 can be considered, but it is particularly preferable to return to the inlet side of the activated carbon tower 3 as shown in the figure. That is, when it is returned to the raw water line, the water to be treated in the deaeration device 2 increases, which is uneconomical. There is no such problem when returned to the outlet side of the activated carbon tower 3, but it is returned to the inlet side of the activated carbon tower 3 and treated with activated carbon, so that the pH fluctuation range is suppressed by the pH stabilization action by the activated carbon treatment. Is very advantageous.

なお、図１では、ＲＯ処理のｐＨ調整を第１ＲＯ装置４の入口側と第２ＲＯ装置５の入口側の双方で行うが、このｐＨ調整は、第１ＲＯ装置４の入口側のみ、或いは、第２ＲＯ装置５の入口側のみで行っても良い。   In FIG. 1, the pH adjustment of the RO treatment is performed on both the inlet side of the first RO device 4 and the inlet side of the second RO device 5. This pH adjustment is performed only on the inlet side of the first RO device 4 or on the first side. It may be performed only on the entrance side of the 2RO device 5.

第１ＲＯ装置４の入口側でｐＨ調整すると、原水中の塩類の大部分を除去する第１ＲＯ装置４が最適条件となるため、効率的な処理を行える。また、第２ＲＯ装置５の入口側でｐＨ調整すると、この水は、第１ＲＯ装置４で塩類の大部分が除去されているため、水中のイオンの影響を受けることなく容易にｐＨ調整することができ、ｐＨ調整のための酸又はアルカリが少量で足りるという利点がある。   When the pH is adjusted on the inlet side of the first RO device 4, the first RO device 4 that removes most of the salt in the raw water is in an optimal condition, and therefore, efficient processing can be performed. Further, when the pH is adjusted on the inlet side of the second RO device 5, since most of the salt is removed from the water by the first RO device 4, the pH can be easily adjusted without being affected by ions in the water. There is an advantage that a small amount of acid or alkali for pH adjustment is sufficient.

図１の如く、第１ＲＯ装置４の入口側と第２ＲＯ装置５の入口側の両方でｐＨ調整した場合には、上記効果を共に得ることができる上に、一方のｐＨ調整手段にトラブルが発生した場合でも、他方のｐＨ調整手段でこれを補って、水質を安定化することができる。   As shown in FIG. 1, when the pH is adjusted on both the inlet side of the first RO device 4 and the inlet side of the second RO device 5, both of the above effects can be obtained and a trouble occurs in one pH adjusting means. Even in this case, the water quality can be stabilized by supplementing this with the other pH adjusting means.

本発明において、ＲＯ処理のＲＯ膜としては、各ＲＯ装置共に、脱塩率の高いＲＯ膜、特に脱塩率９９．５％以上のＲＯ膜を使用するのが好ましい。   In the present invention, as the RO membrane for RO treatment, it is preferable to use an RO membrane having a high desalting rate, particularly an RO membrane having a desalting rate of 99.5% or more for each RO device.

特に、図１に示す如く、３段ＲＯ処理する場合、第３ＲＯ装置６に流入する第２ＲＯ装置５の透過水は、既に２段階のＲＯ処理を経ることで、十分に純度が高められたものである。このように純度の高い第２ＲＯ装置５の透過水をＲＯ処理する第３ＲＯ装置６のＲＯ膜としては、低塩類濃度域における脱塩率の高いＲＯ膜を用いるのが好ましい。このようなＲＯ膜であれば、２段ＲＯ処理により既にイオン濃度が相当に低減された第２ＲＯ装置の透過水中のイオンを極低濃度にまで除去して、著しく高水質の処理水を得ることができる。   In particular, as shown in FIG. 1, in the case of a three-stage RO treatment, the permeated water of the second RO apparatus 5 flowing into the third RO apparatus 6 has already been sufficiently subjected to the two-stage RO treatment to sufficiently increase the purity. It is. As the RO membrane of the third RO device 6 that performs RO treatment on the permeated water of the second RO device 5 having a high purity as described above, it is preferable to use an RO membrane having a high desalination rate in a low salt concentration range. With such an RO membrane, the ion in the permeated water of the second RO device, whose ion concentration has already been considerably reduced by the two-stage RO treatment, is removed to an extremely low concentration, and a remarkably high quality treated water can be obtained. Can do.

従って、この第３段ＲＯ装置６のＲＯ膜としては、正に荷電したＲＯ膜を使用する。 Therefore, the RO membrane of the third stage RO device 6, to use a positively charged RO membranes.

即ち、前述の如く、第１ＲＯ装置４では原水中の塩類、ＴＯＣの殆どが除去され、第２ＲＯ装置５では特に残留アニオンが除去される。従って、第３ＲＯ装置６では、カチオンを反発してカチオンを効果的に除去する正荷電膜を用い、特に残留カチオンを効率的に除去する。 That is, as described above, the first RO device 4 removes most of the salts and TOC in the raw water, and the second RO device 5 particularly removes residual anions. Therefore, in the 3RO device 6, using a positively charged membrane to effectively remove the cations and repel cations, particularly efficiently remove residual cation.

なお、通常のＲＯ膜は負荷電膜が一般的であり、アニオン除去効果が高い。   A normal RO membrane is generally a negatively charged membrane and has a high anion removal effect.

本発明において３段ＲＯ処理を行う場合、第１ＲＯ装置及び第２ＲＯ装置のＲＯ膜としては、日東電工株式会社製「ＥＳ２０」、東レ株式会社製「ＳＵ９１０」等の負荷電膜を用いるのが好ましい。また、第３ＲＯ装置のＲＯ膜としては、塩類濃度１〜１０ｐｐｍというような低塩類濃度域における脱塩率が９９％以上のＲＯ膜、例えば、日東電工社製「ＮＴＲ−７１９ＨＦ」，「ＥＳ１０Ｃ」（共にＮａＣｌ濃度１〜１０ｐｐｍでのＮａＣｌ阻止率９９％以上）等の正荷電膜を用いる。 When performing the three-stage RO treatment in the present invention, it is preferable to use a load membrane such as “ES20” manufactured by Nitto Denko Corporation, “SU910” manufactured by Toray Industries, Inc. as the RO membrane of the first RO device and the second RO device. . Further, as the RO membrane of the third RO device, an RO membrane having a desalination rate of 99% or more in a low salt concentration region such as a salt concentration of 1 to 10 ppm, for example, “NTR-719HF” and “ES10C” manufactured by Nitto Denko Corporation. Ru used (both NaCl rejection of 99% or more at a NaCl concentration 1-10 ppm) positively charged membrane, such as.

なお、図１には、３段ＲＯ処理を行う例を示したが、本発明では３段ＲＯ処理を行うことにより、一層の高純度化が図れ、従来の一次純水装置で用いられているイオン交換装置を省略することができるため、３段ＲＯ処理とする。 In addition, although the example which performs 3 step | paragraph RO processing was shown in FIG. 1, in this invention, further refinement | purification can be achieved by performing 3 step | paragraph RO processing, and it is used with the conventional primary pure water apparatus. Since the existing ion exchange device can be omitted , the three- stage RO treatment is adopted.

即ち、イオン交換装置を必要とする場合には、イオン交換樹脂の再生のための操作や薬剤、再生廃液の処理が必要となり、装置や操作が複雑となる上に、コストが高騰する。従って、３段ＲＯ処理を採用してイオン交換装置を省略するのが有利である。   That is, when an ion exchange device is required, an operation for regeneration of the ion exchange resin, treatment of chemicals and regeneration waste liquid are required, and the device and operation become complicated and the cost increases. Therefore, it is advantageous to adopt a three-stage RO process and omit the ion exchange device.

ただし、３段ＲＯ処理を採用した場合でも、より高純度の純水が必要とされる場合には、小容量の非再生型イオン交換装置で処理した後、サブシステムに送るようにしても良い。   However, even when the three-stage RO treatment is adopted, if pure water with higher purity is required, it may be sent to the subsystem after being treated with a small-capacity non-regenerative ion exchanger. .

以下に実施例及び比較例を挙げて本発明をより具体的に説明する。   Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

実施例１
図１に示す方法に従って、水道水と半導体工場の回収水とを水道水：回収水＝３：７で混合した水（全炭酸濃度４．３ｐｐｍ）を原水として処理を行った。この水の３段ＲＯ処理の好適ｐＨ値は、図４に示す如く、約ｐＨ６．０〜６．１である。 Example 1
In accordance with the method shown in FIG. 1, treatment was performed using tap water and water collected from a semiconductor factory mixed with tap water: recovered water = 3: 7 (total carbon dioxide concentration 4.3 ppm) as raw water. A suitable pH value for the three-stage RO treatment of water is about pH 6.0 to 6.1 as shown in FIG.

まず、原水に酸（Ｈ₂ＳＯ₄）を添加してｐＨ４．７〜４．８にした後、膜脱気装置（大日本インキ工業社製「ＳＥＰＡＲＥＬ ＥＦ０４０Ｐ」）２に通水し、真空ポンプ（リーチャリー社製「ＶＣＥ−４０」）で吸引した。その後、活性炭（ＣＷ１０／３２）塔３にＳＶ＝２０ｈｒ^-1で通水した。 First, acid (H ₂ SO ₄ ) was added to the raw water to adjust the pH to 4.7 to 4.8, and then passed through a membrane deaerator (“SEPAREL EF040P” 2 manufactured by Dainippon Ink & Chemicals, Inc.) 2 to obtain a vacuum pump (Veach-40 “VCE-40”). Thereafter, water was passed through the activated carbon (CW10 / 32) tower 3 at SV = 20 hr ⁻¹ .

活性炭塔３の出口水のｐＨは６．０〜６．１であったので、この水をｐＨ調整することなくそのまま、高圧ポンプＰ−５で運転圧１５ｋｇ／ｃｍ²で３段ＲＯ処理した。用いたＲＯ膜は、第１ＲＯ装置４及び第２ＲＯ装置５では日東電工社製ポリアクリルアミドＲＯ膜「ＥＳ−２０」（４インチ）であり、第３ＲＯ装置６では日東電工社製ポリアクリルアミドＲＯ膜「ＥＳ１０Ｃ」である。 Since the pH of the outlet water of the activated carbon tower 3 was 6.0 to 6.1, the water was subjected to three-stage RO treatment with the high pressure pump P-5 at an operating pressure of 15 kg / cm ² without adjusting the pH. The RO membrane used is the polyacrylamide RO membrane “ES-20” (4 inches) manufactured by Nitto Denko in the first RO device 4 and the second RO device 5, and the polyacrylamide RO membrane manufactured by Nitto Denko in the third RO device 6. ES10C ".

その結果、第３ＲＯ装置の透過水として、比抵抗１６〜１７ＭΩ／ｃｍの高純度の純水を安定に得ることができた。   As a result, high-purity pure water having a specific resistance of 16 to 17 MΩ / cm could be stably obtained as the permeated water of the third RO device.

なお、この実施例における原水タンク１の出口水のｐＨ，活性炭塔３の出口水のｐＨ及び得られた純水の比抵抗の経時変化を図５に示す。   In addition, FIG. 5 shows changes over time in the pH of the outlet water of the raw water tank 1, the pH of the outlet water of the activated carbon tower 3, and the specific resistance of the obtained pure water in this example.

比較例１
実施例１において、脱気処理水を活性炭塔に通水せずに直接ｐＨ調整して３段ＲＯ処理したこと以外は同様にして処理を行った。 Comparative Example 1
In Example 1, the treatment was performed in the same manner except that the degassed treated water was directly adjusted to pH without passing through the activated carbon tower and subjected to the three-stage RO treatment.

その結果、脱気処理水のｐＨは５．２〜５．８の範囲で大きく変動し、この脱気処理水にＮａＯＨを添加してｐＨ６．０〜６．１に調整したものの、３段ＲＯ処理の給水のｐＨは結果的にｐＨ５．９〜６．５の間で変動したため、得られた純水の比抵抗は６〜１６ＭΩ／ｃｍとなった。   As a result, the pH of the degassed treated water greatly fluctuated in the range of 5.2 to 5.8, and NaOH was added to this degassed treated water to adjust the pH to 6.0 to 6.1. As a result, the pH of the treated feed water varied between pH 5.9 and 6.5, and the specific resistance of the obtained pure water was 6 to 16 MΩ / cm.

本発明の純水の製造方法の実施の形態を示す系統図である。It is a systematic diagram which shows embodiment of the manufacturing method of the pure water of this invention. 膜脱気装置の入口水と出口水のｐＨ変動を示すグラフである。It is a graph which shows the pH fluctuation | variation of the inlet water and outlet water of a membrane deaeration apparatus. ３段ＲＯ処理の給水のｐＨと得られる処理水の比抵抗との関係を示すグラフである。It is a graph which shows the relationship between the pH of the water supply of a three-stage RO process, and the specific resistance of the treated water obtained. ３段ＲＯ処理の給水のｐＨと得られる処理水の比抵抗との関係を示すグラフである。It is a graph which shows the relationship between the pH of the water supply of a three-stage RO process, and the specific resistance of the treated water obtained. 実施例１における原水タンク１の出口水のｐＨ，活性炭塔３の出口水のｐＨ及び得られた純水の低抵抗の経時変化を示すグラフである。It is a graph which shows the time-dependent change of pH of the outlet water of the raw | natural water tank 1 in Example 1, the pH of the outlet water of the activated carbon tower 3, and the low resistance of the obtained pure water.

符号の説明Explanation of symbols

１ 原水タンク
２ 脱気装置
３ 活性炭塔
４ 第１ＲＯ装置
５ 第２ＲＯ装置
６ 第３ＲＯ装置
Ｐ−１，Ｐ−２，Ｐ−３，Ｐ−４，Ｐ−６，Ｐ−７ ポンプ
Ｐ−５ 高圧ポンプ
Ｍ−１，Ｍ−２，Ｍ−３ 撹拌機
Ｈ−１，Ｈ−２，Ｈ−３ ｐＨ計 DESCRIPTION OF SYMBOLS 1 Raw water tank 2 Deaeration apparatus 3 Activated carbon tower 4 1st RO apparatus 5 2nd RO apparatus 6 3rd RO apparatus P-1, P-2, P-3, P-4, P-6, P-7 Pump P-5 High pressure Pump M-1, M-2, M-3 Stirrer H-1, H-2, H-3 pH meter

Claims (1)

被処理水に酸を添加して脱気処理した後、多段に直列配置した逆浸透膜分離装置に順次通水して純水を製造する方法において、脱気処理後の水を活性炭と接触させ、該活性炭接触後の水を多段に直列配置した前記逆浸透膜分離装置に順次通水することを特徴とする純水の製造方法。   In the method of producing pure water by adding water to the water to be treated and degassing it, and then sequentially passing through the reverse osmosis membrane separators arranged in series in multiple stages, the degassed water is brought into contact with activated carbon. The water after contacting the activated carbon is sequentially passed through the reverse osmosis membrane separation device arranged in series in multiple stages.

Images