JP5121982B2

JP5121982B2 - Electrodialysis system

Info

Publication number: JP5121982B2
Application number: JP2011138600A
Authority: JP
Inventors: 剛士阿部; 浩行森弘
Original assignee: Astom Corp
Current assignee: Astom Corp
Priority date: 2011-06-22
Filing date: 2011-06-22
Publication date: 2013-01-16
Anticipated expiration: 2031-06-22
Also published as: JP2013006128A

Description

本発明は、それに限定されるものではないが、埋立地からの浸出水を脱イオン、特に脱クロロイオン、濃縮処理するのに好適に使用することができる電気透析システムに関する。 Although this invention is not limited to it, It is related with the electrodialysis system which can be used suitably for deionizing especially the leachate from a landfill site, especially a dechloroion ion, and a concentration process.

例えば埋立地からの浸出水は、周知の如く、埋立に使用された廃棄物等に起因して相当量のイオン、特にクロロイオンを含有しており、そのまま河川に排出或いは農業用水として利用すると、生態系の破壊を引き起こし或いは農作物に悪影響を及ぼす。従って、埋立地からの浸出水を、河川に排出或いは農業用水として使用するのに先立って、脱イオン、特に脱クロロイオン、濃縮処理を加えてイオン濃度が充分に低い脱イオン水とイオン濃度が充分に高い濃縮水を生成することが必要である。 For example, leachate from landfills, as is well known, contains a considerable amount of ions, especially chloro ions, due to wastes used for landfill, etc. Causes ecosystem destruction or adversely affects crops. Therefore, before the leachate from the landfill is discharged into the river or used as agricultural water, deionized water and ion concentration are sufficiently low by adding deionization, especially dechloroion and concentration treatment. It is necessary to produce a sufficiently high concentrated water.

下記特許文献１乃至３には、埋立地からの浸出水の脱イオン濃縮処理に使用することができる電気透析システムが開示されている。通常、生成された濃縮水は加熱乾燥装置に送給されて加熱固化され、塩が生成される。加熱乾燥装置を効率的に運転せしめるためには、供給する濃縮水のクロロイオン濃度は所定高濃度、例えば１００，０００ｐｐｍ程度、以上であることが重要である。そこで、下記特許文献２に開示されている電気透析システムにおいては、電気透析システムから排出される濃縮水のイオン濃度が所定高濃度より低い場合には、加熱乾燥装置に送給することなく、電気透析システムに還流せしめて再び脱イオン・濃縮処理を施している。また、上記特許文献３に開示されている電気透析システムにおいては、電気透析システムから排出される濃縮水のＣｌ⁻／Ｃａ^２＋が所定値以下の場合には、加熱乾燥装置に送給する濃度まで濃縮することなく、電気透析システムに還流せしめて再び脱イオン・濃縮処理を施している。 Patent Documents 1 to 3 below disclose an electrodialysis system that can be used for deionization and concentration treatment of leachate from a landfill. Usually, the produced | generated concentrated water is sent to a heat drying apparatus, and is solidified by heating, and a salt is produced | generated. In order to efficiently operate the heating and drying apparatus, it is important that the chloroion concentration of the concentrated water to be supplied is a predetermined high concentration, for example, about 100,000 ppm or more. Therefore, in the electrodialysis system disclosed in Patent Document 2 below, when the ion concentration of the concentrated water discharged from the electrodialysis system is lower than a predetermined high concentration, the electric dialysis system does not feed the heating and drying apparatus. The dialysis system is refluxed and deionized and concentrated again. Further, in the electrodialysis system disclosed in Patent Document 3, when the concentration of Cl ⁻ / Ca ²⁺ discharged from the electrodialysis system is equal to or lower than a predetermined value, the concentration to be supplied to the heating and drying apparatus is reached. Without concentration, it is refluxed to the electrodialysis system and again subjected to deionization and concentration treatment.

特開平５−２７７４９２号公報JP-A-5-277492 特開平１０−８０６８８号公報Japanese Patent Laid-Open No. 10-80688 特開２００１−１７８３８号公報JP 2001-17838 A

而して、当業者には周知の如く、例えば埋立地からの浸出水は雨水の混入等に起因してイオン濃度が相当大幅に変動するが、従来の電気透析システムにおいては、イオン濃度の変動に起因して脱イオン・濃縮処理効率が大幅に変動してしまう、更に詳述すると、イオン濃度の必要低減率が所定範囲を超えて増大すると、脱イオン・濃度処理効率が大幅に低減してしまう。また、イオンの移動に付随して水和水等の付随水の移動が発生すること、及びイオン交換膜を挟んだ脱イオン水側と濃縮水側との間の濃度差（浸透圧）に起因して脱イオン側から濃縮水側に浸透水が移動すること、に起因して濃縮水濃度が制限される。 Thus, as is well known to those skilled in the art, for example, leachate from landfills varies considerably in ion concentration due to contamination of rainwater, but in conventional electrodialysis systems, fluctuations in ion concentration occur. Deionization / concentration treatment efficiency will fluctuate significantly due to the fact that the deionization / concentration treatment efficiency will be greatly reduced if the necessary reduction rate of the ion concentration exceeds the specified range. End up. In addition, the accompanying water movement such as hydration water occurs accompanying the movement of ions, and the concentration difference (osmotic pressure) between the deionized water side and the concentrated water side across the ion exchange membrane. Thus, the concentration of the concentrated water is limited due to the permeated water moving from the deionized side to the concentrated water side.

本発明は上記事実に鑑みてなされたものであり、その主たる技術的課題は、埋立地からの浸出水の如き被処理水のイオン濃度が相当大幅に変動しても、電力消費コストを含む作動コストを必要最小限度に抑制して、脱イオン・濃縮処理効率を高効率に維持することができると共に、必要に応じて高濃度の濃縮水を得ることができる、新規且つ改良された電気透析システムを提供することである。 The present invention has been made in view of the above facts, and its main technical problem is that even if the ion concentration of water to be treated such as leachate from a landfill fluctuates considerably, operation including power consumption cost is required. A new and improved electrodialysis system that can keep the deionization / concentration efficiency high while keeping costs at a minimum level and can obtain concentrated water with high concentration as required. Is to provide.

本発明者等は、鋭意研究及び実験の結果、少なくとも２台の電気透析装置を直列配置し、最上流に位置する最上流電気透析装置に付設された最上流脱イオン水槽に被処理水を供給し、最上流電気透析装置に付設された最上流濃縮水槽から濃縮水を流出せしめ、最下流に位置する最下流電気透析装置に付設された脱イオン水槽から脱イオン水を流出せしめられ、そして更に被処理水の電導度に応じて作動せしめる電気透析装置の台数を設定することによって、上記主たる技術的課題を達成することができることを見出した。 As a result of diligent research and experiments, the present inventors have arranged at least two electrodialyzers in series, and supply treated water to the most upstream deionized water tank attached to the most upstream electrodialysis device. The concentrated water is allowed to flow out from the most upstream concentrated water tank attached to the most upstream electrodialysis apparatus, and the deionized water is allowed to flow out from the deionized water tank attached to the most downstream electrodialysis apparatus located downstream. It has been found that the main technical problem can be achieved by setting the number of electrodialyzers to be operated according to the conductivity of the water to be treated.

即ち、本発明によれば、上記主たる技術的課題を達成する電気透析システムとして、直列配列された少なくとも２台の電気透析装置と共に、脱イオン・濃縮すべき被処理水を供給するための被処理水供給手段及び制御手段を備え、
該被処理水供給手段は最上流に位置する最上流電気透析装置に付設された最上流脱イオン水槽に被処理水を供給し、該最上流電気透析装置に付設された最上流濃縮水槽から濃縮水が流出せしめられ、最下流に位置する最下流電気透析装置に付設された脱イオン水槽から脱イオン水が流出せしめられ、
該制御手段は、被処理水の電導度に応じて、作動せしめる電気透析装置の台数を設定する、
ことを特徴とする電気透析システムが提供される。 In other words, according to the present invention, as an electrodialysis system that achieves the main technical problem described above, along with at least two electrodialyzers arranged in series, to-be-treated for supplying water to be deionized and concentrated Water supply means and control means,
The treated water supply means supplies treated water to the most upstream deionized water tank attached to the most upstream electrodialysis apparatus located at the most upstream, and concentrates from the most upstream concentrated water tank attached to the most upstream electrodialysis apparatus. Water was allowed to flow out, and deionized water was allowed to flow out from the deionized water tank attached to the most downstream electrodialysis apparatus located at the most downstream,
The control means sets the number of electrodialyzers to be activated according to the conductivity of the water to be treated.
An electrodialysis system is provided.

好ましくは、該制御手段は、被処理水の電導度が所定値以下の場合には該最下流電気透析装置のみを作動せしめ、被処理水の電導度の上昇に応じて、下流側から上流側に向けて漸次電気透析装置の作動台数を増大せしめる。該最下流電気透析装置は極性転換方式であり、他の電気透析装置は非極性転換方式であるのが好適である。該最上流電気透析装置に付設された該濃縮水槽から流出せしめられる濃縮水は所定高濃度以上のイオン濃度を有し、該最下流電気透析装置から流出せしめられる脱イオン水は所定低濃度以下のイオン濃度を有するのが好都合である。好適実施形態においては、該最上流電気透析装置及び該最下流電気透析装置に加えて、該最上流電気透析装置と該最下流電気透析装置との間に位置する少なくとも１台の中間電気透析装置を含み、
該最上流電気透析装置には、該最上流脱イオン水槽内の脱イオン水を該最上流電気透析装置の脱イオン室に送給すると共に該最上流電気透析装置において脱イオンされた脱イオン水を該最上流脱イオン水槽に返送するための最上流脱イオン水ポンプ手段と、該最上流濃縮水槽内の濃縮水を該最上流電気透析装置の濃縮室に送給すると共に該最上流電気透析装置において濃縮された濃縮水を該最上流濃縮水槽に返送するための最上流濃縮水ポンプ手段とが付設されており、
該中間電気透析装置には、中間脱イオン水槽と、中間濃縮水槽と、該中間脱イオン水槽内の脱イオン水を該中間電気透析装置の脱イオン室に送給すると共に該中間電気透析装置において脱イオンされた脱イオン水を該中間脱イオン水槽に返送するための中間脱イオン水ポンプ手段と、該中間濃縮水槽内の濃縮水を該中間電気透析装置の濃縮室に送給すると共に該中間電気透析装置において濃縮された濃縮水を該中間濃縮水槽に返送するための中間濃縮水ポンプ手段とが付設されており、
該最下流電気透析装置には、最下流脱イオン水槽と、最下流濃縮水槽と、該最下流脱イオン水槽内の脱イオン水を該最下流電気透析装置の脱イオン室に送給すると共に該最下流電気透析装置において脱イオンされた脱イオン水を該最下流脱イオン水槽に返送するための最下流脱イオン水ポンプ手段と、該最下流濃縮水槽内の濃縮水を該最下流電気透析装置の濃縮室に送給すると共に該最下流電気透析装置において濃縮された濃縮水を該最下流濃縮水槽に返送するための最下流濃縮水ポンプ手段とが付設されており、
該最上流脱イオン水槽をオーバーフローした脱イオン水が該中間脱イオン水槽に流動せしめられ、そして該中間脱イオン水槽をオーバーフローした脱イオン水が該最下流脱イオン水槽に流動せしめられ、該最下流電気透析装置の該脱イオン室を通して循環せしめられる脱イオン水の循環路からオーバーフローした脱イオン水は該最下流濃縮水槽に流動せしめられ、
該最下流濃縮水槽をオーバーフローした濃縮水は該中間濃縮水槽に流動せしめられ、該中間濃縮水槽からオーバーフローした濃縮水は該被処理水供給手段に返流せしめられる。該中間濃縮水槽からオーバーフローした濃縮水は該被処理水供給手段に返流せしめられるのに先立ってカルシウム除去手段に送給されてカルシウム除去処理を受けるのが好適である。 Preferably, the control means activates only the most downstream electrodialysis apparatus when the conductivity of the water to be treated is a predetermined value or less, and from the downstream side to the upstream side according to the increase in the conductivity of the water to be treated. Gradually increase the number of electrodialyzers operated. It is preferable that the most downstream electrodialysis apparatus is a polarity conversion system, and the other electrodialysis apparatus is a nonpolar conversion system. Concentrated water discharged from the concentrated water tank attached to the most upstream electrodialysis apparatus has an ion concentration of a predetermined high concentration or more, and deionized water discharged from the most downstream electrodialysis apparatus has a predetermined low concentration or less. Conveniently having an ionic concentration. In a preferred embodiment, in addition to the most upstream electrodialysis apparatus and the most downstream electrodialysis apparatus, at least one intermediate electrodialysis apparatus positioned between the most upstream electrodialysis apparatus and the most downstream electrodialysis apparatus. Including
The most upstream electrodialysis apparatus supplies deionized water in the most upstream deionized water tank to the deionization chamber of the most upstream electrodialysis apparatus and deionized water deionized in the most upstream electrodialysis apparatus. The most upstream deionized water pump means for returning the concentrated water in the most upstream deionized water tank, and the concentrated water in the most upstream concentrated water tank is fed to the concentrating chamber of the most upstream electrodialysis apparatus and the most upstream electrodialysis An uppermost stream concentrated water pump means for returning the concentrated water concentrated in the apparatus to the uppermost stream concentrated water tank;
In the intermediate electrodialysis apparatus, an intermediate deionized water tank, an intermediate concentrated water tank, and deionized water in the intermediate deionized water tank are supplied to the deionization chamber of the intermediate electrodialysis apparatus and in the intermediate electrodialysis apparatus Intermediate deionized water pump means for returning deionized deionized water to the intermediate deionized water tank, and the concentrated water in the intermediate concentrated water tank are fed to the concentration chamber of the intermediate electrodialyzer and the intermediate An intermediate concentrated water pump means for returning the concentrated water concentrated in the electrodialyzer to the intermediate concentrated water tank is attached,
The most downstream electrodialyzer supplies the most downstream deionized water tank, the most downstream concentrated water tank, and the deionized water in the most downstream deionized water tank to the deionized chamber of the most downstream electrodialyzer and The most downstream deionized water pump means for returning deionized water deionized in the most downstream electrodialyzer to the most downstream deionized water tank, and the concentrated water in the most downstream concentrated water tank is used as the most downstream electrodialyzer. And the most downstream concentrated water pump means for returning the concentrated water concentrated in the most downstream electrodialyzer to the most downstream concentrated water tank,
The deionized water that has overflowed the most upstream deionized water tank is caused to flow into the intermediate deionized water tank, and the deionized water that has overflowed the intermediate deionized water tank is caused to flow into the most downstream deionized water tank, and the most downstream The deionized water overflowed from the deionized water circulation path circulated through the deionization chamber of the electrodialyzer is caused to flow into the most downstream concentrated water tank,
The concentrated water overflowing the most downstream concentrated water tank is caused to flow into the intermediate concentrated water tank, and the concentrated water overflowing from the intermediate concentrated water tank is returned to the treated water supply means. The concentrated water overflowed from the intermediate concentrated water tank is preferably supplied to the calcium removing means and subjected to the calcium removing treatment before being returned to the treated water supply means.

本発明の電気透析システムにおいては、被処理水の電導度に応じて作動せしめる電気透析装置の台数が設定される。従って、被処理水の電導度が大幅に変動しても、電力消費コストを含む作動コストを必要最小限度に抑制して、各電気透析装置において被処理水の低減すべき電導度即ちイオン濃度を所定範囲に維持することができ、かくして各電気透析装置を充分高効率で作動せしめることができる。そしてまた、最上流電気透析装置に付設された濃縮水槽以外の濃縮水槽中の濃縮水は排出されることなく、例えば被処理水供給手段に返送され、脱イオン水側のイオン濃度が最も高い最上流電気透析装置に付設された濃縮水槽中の濃縮水のみが排出される故に、排出される濃縮水の濃度を所要とおりの高濃度にせしめることができる。 In the electrodialysis system of the present invention, the number of electrodialyzers to be operated is set according to the conductivity of the water to be treated. Therefore, even if the conductivity of the water to be treated fluctuates greatly, the operating cost including the power consumption cost is suppressed to the minimum necessary, and the conductivity, that is, the ion concentration to be reduced in each electrodialyzer is reduced. Thus, the electrodialysis apparatus can be operated with sufficiently high efficiency. Further, the concentrated water in the concentrated water tanks other than the concentrated water tank attached to the most upstream electrodialysis apparatus is not discharged, but is returned to the treated water supply means, for example, and the ion concentration on the deionized water side is the highest. Since only the concentrated water in the concentrated water tank attached to the upstream electrodialysis apparatus is discharged, the concentration of the discharged concentrated water can be made as high as required.

本発明に従って構成された電気透析システムの好適実施形態を示す間略図。1 is a schematic diagram illustrating a preferred embodiment of an electrodialysis system constructed in accordance with the present invention. 図1に示す電気透析システムにおける電気透析装置の作動台数設定手順を示すフローチャート。2 is a flowchart showing a procedure for setting the number of electrodialyzers in the electrodialysis system shown in FIG. 図１に示す電気透析システムにおける最上流電気透析装置の作動制御手順を示すフローチャート。The flowchart which shows the operation | movement control procedure of the most upstream electrodialysis apparatus in the electrodialysis system shown in FIG. 図１に示す電気透析システムにおける中間電気透析装置の作動制御手順を示すフローチャート。The flowchart which shows the operation | movement control procedure of the intermediate | middle electrodialysis apparatus in the electrodialysis system shown in FIG. 図1に示す電気透析システムにおける最下流電気透析装置の作動制御手順を示すフローチャート。2 is a flowchart showing an operation control procedure of the most downstream electrodialysis apparatus in the electrodialysis system shown in FIG.

図１を参照して説明すると、本発明に従って構成された図示の電気透析システムは、脱イオン・濃縮すべき被処理水を供給するための被処理水供給手段２、直列配列された３台の電気透析装置、即ち最上流電気透析装置４、中間電気透析装置６及び最下流電気透析装置８、並びに記憶手段を内蔵したマイクロプロセッサから構成することができる制御手段（図示していない）を備えている。所望ならば、中間電気透析装置６を省略して２台の電気透析装置、即ち最上流電気透析装置４及び最下流電気透析装置８、を装備し、或いは最上流電気透析装置４及び最下流電気透析装置８に加えて２台又はそれ以上の中間電気透析装置を装備することもできる。 Referring to FIG. 1, the illustrated electrodialysis system constructed in accordance with the present invention includes treated water supply means 2 for supplying treated water to be deionized and concentrated, and three units arranged in series. An electrodialyzer, that is, a most upstream electrodialyzer 4, an intermediate electrodialyzer 6, and a most downstream electrodialyzer 8, and control means (not shown) which can be constituted by a microprocessor incorporating a memory means. Yes. If desired, the intermediate electrodialyzer 6 may be omitted and equipped with two electrodialyzers, namely the most upstream electrodialyzer 4 and the most downstream electrodialyzer 8, or the most upstream electrodialyzer 4 and the most downstream electrodialyzer. In addition to the dialyzer 8, two or more intermediate electrodialyzers can be provided.

被処理水供給手段２は被処理水タンク１０、被処理水供給ポンプ手段１２及び電導度計１４を含んでいる。被処理水タンク１０には、例えば埋立地からの浸出水である、脱イオン・濃縮すべき被処理水が適宜の導入手段（図示していない）によって導入される。被処理水供給ポンプ手段１２は被処理水タンク１０内の被処理水を供給ライン１６に流出せしめる。電導度計１４は供給ライン１６を流動する被処理水の電導度即ちイオン濃度を測定する。 The treated water supply means 2 includes a treated water tank 10, a treated water supply pump means 12, and a conductivity meter 14. The treated water to be deionized and concentrated, for example, leachate from a landfill, is introduced into the treated water tank 10 by appropriate introduction means (not shown). The treated water supply pump means 12 causes the treated water in the treated water tank 10 to flow out to the supply line 16. The conductivity meter 14 measures the conductivity, that is, the ion concentration, of the water to be treated flowing through the supply line 16.

最上流電気透析装置４は、脱イオン室１８と濃縮室２０とを有する通常形態、即ち非極性転換方式（脱イオン室１８と濃縮室２０とが転換されることがない方式）の、それ自体は周知の電気透析装置から構成されている。最上流電気透析装置４の脱イオン室１８には、最上流脱イオン水槽２２、最上流脱イオン水ポンプ手段２４及び電導度計２６が付設されている。最上流脱イオン水槽２２には上記被処理水タンク１０から上記供給ライン１６を通して被処理水が供給される。最上流脱イオン水ポンプ手段２４は、最上流脱イオン水槽２２から脱イオン水を流出せしめて送給ライン２８を通して脱イオン室１８に送給すると共に、脱イオン室１８から返送ライン３０を通して最上流脱イオン水槽２２に脱イオン水を返送する。電導度計２６は返送ライン３０を流動する脱イオン水の電導度を測定する。脱イオン水槽２２にはオーバーフローする脱イオン水の流動ライン３２も配設されている。最上流電気透析装置４の濃縮室２０には、最上流濃縮水槽３４、最上流濃縮水ポンプ手段３６、電導度計３８及びｐＨ計４０が付設されている。最上流濃縮水槽３４には上記供給ライン１６から分岐する分岐供給ライン４２を介して上記被処理水タンク１０から被処理水が供給される。最上流濃縮水ポンプ手段３６は、最上流濃縮水槽３４から濃縮水を流出せしめて送給ライン４４を通して濃縮室２０に送給すると共に、濃縮室２０から返送ライン４６を通して最上流濃縮水槽３４に濃縮水を返送する。電導度計３８は返送ライン４６を流動する濃縮水の電導度を計測し、ｐＨ計４０は返送ライン４６を流動する濃縮水のｐＨを計測する。最上流濃縮水槽３４には濃縮水流出ライン４８も配設されており、この濃縮水流出ライン４８は濃縮水受槽５０まで延びている。 The most upstream electrodialysis apparatus 4 itself has a normal configuration having a deionization chamber 18 and a concentration chamber 20, that is, a nonpolar conversion method (a method in which the deionization chamber 18 and the concentration chamber 20 are not converted). Is constituted by a known electrodialysis apparatus. In the deionization chamber 18 of the most upstream electrodialysis apparatus 4, a most upstream deionized water tank 22, a most upstream deionized water pump means 24, and a conductivity meter 26 are attached. To-be-treated water is supplied to the most upstream deionized water tank 22 from the to-be-treated water tank 10 through the supply line 16. The most upstream deionized water pump means 24 drains deionized water from the most upstream deionized water tank 22 and feeds it to the deionization chamber 18 through the feed line 28, and from the deionization chamber 18 through the return line 30. The deionized water is returned to the deionized water tank 22. The conductivity meter 26 measures the conductivity of deionized water flowing through the return line 30. The deionized water tank 22 is also provided with a flow line 32 of overflowing deionized water. The concentration chamber 20 of the most upstream electrodialysis apparatus 4 is provided with a most upstream concentrated water tank 34, a most upstream concentrated water pump means 36, a conductivity meter 38 and a pH meter 40. Water to be treated is supplied from the water tank 10 to be treated to the uppermost concentrated water tank 34 via a branch supply line 42 branched from the supply line 16. The most upstream concentrated water pump means 36 discharges concentrated water from the most upstream concentrated water tank 34 and feeds it to the concentrating chamber 20 through the feeding line 44 and concentrates it from the concentrating chamber 20 to the most upstream concentrated water tank 34 through the returning line 46. Return the water. The conductivity meter 38 measures the conductivity of the concentrated water flowing through the return line 46, and the pH meter 40 measures the pH of the concentrated water flowing through the return line 46. A concentrated water outflow line 48 is also provided in the uppermost stream concentrated water tank 34, and this concentrated water outflow line 48 extends to the concentrated water receiving tank 50.

中間電気透析装置６は、上記最上流電気透析装置４と同様に、脱イオン室５２と濃縮室５４とを有する非極性転換方式の、それ自体は周知の電気透析装置から構成されている。中間電気透析装置６の脱イオン室５２には、中間脱イオン水槽５６、中間脱イオン水ポンプ手段５８及び電導度計６０が付設されている。中間脱イオン水槽５６には上記流動ライン３２を介して上記最上流脱イオン水槽２２をオーバーフローする脱イオン水が供給される。中間脱イオン水ポンプ手段５８は、中間脱イオン水槽５６から脱イオン水を流出せしめて送給ライン６２を通して脱イオン室５２に送給すると共に、脱イオン室５２から返送ライン６４を通して中間脱イオン水槽５６に脱イオン水を返送する。電導度計６０は返送ライン６４を流動する脱イオン水の電導度を測定する。中間脱イオン水槽５６にはオーバーフローする脱イオン水の流動ライン６６も配設されている。中間電気透析装置６の濃縮室５４には、中間濃縮水槽６８、中間濃縮水ポンプ手段７０、電導度計７２及びｐＨ計７４が付設されている。中間濃縮水ポンプ手段７０は、中間濃縮水槽６８から濃縮水を流出せしめて送給ライン７６を通して濃縮室５４に送給すると共に、濃縮室５４から返送ライン７８を通して中間濃縮水槽６８に濃縮水を返送する。電導度計７２は返送ライン７８を流動する濃縮水の電導度を計測し、ｐＨ計７４は返送ライン７８を流動する濃縮水のｐＨを計測する。中間濃縮水槽６８にはオーバーフローする濃縮水の流動ライン８０も配設されている。流動ライン８０はカルシウム除去手段８２を介して上記被処理水タンク１０に至る。濃縮水中に析出される難容性塩が実質上皆無或いは比較的小さい少量である場合には、カルシウム除去手段８２を省略することができる。 Similar to the most upstream electrodialysis apparatus 4, the intermediate electrodialysis apparatus 6 is composed of a non-polar conversion type electrodialysis apparatus having a deionization chamber 52 and a concentration chamber 54. In the deionization chamber 52 of the intermediate electrodialysis apparatus 6, an intermediate deionized water tank 56, an intermediate deionized water pump means 58, and a conductivity meter 60 are attached. The deionized water that overflows the uppermost stream deionized water tank 22 is supplied to the intermediate deionized water tank 56 through the flow line 32. The intermediate deionized water pump means 58 discharges deionized water from the intermediate deionized water tank 56 and feeds it to the deionized chamber 52 through the feed line 62, and from the deionized chamber 52 through the return line 64 to the intermediate deionized water tank. Return deionized water to 56. The conductivity meter 60 measures the conductivity of deionized water flowing through the return line 64. The intermediate deionized water tank 56 is also provided with a flow line 66 of deionized water that overflows. An intermediate concentrated water tank 68, an intermediate concentrated water pump means 70, an electric conductivity meter 72 and a pH meter 74 are attached to the concentration chamber 54 of the intermediate electrodialysis apparatus 6. The intermediate concentrated water pump means 70 causes concentrated water to flow out from the intermediate concentrated water tank 68 and supply it to the concentrating chamber 54 through the feeding line 76, and return the concentrated water from the concentrating chamber 54 to the intermediate concentrated water tank 68 through the returning line 78. To do. The conductivity meter 72 measures the conductivity of the concentrated water flowing through the return line 78, and the pH meter 74 measures the pH of the concentrated water flowing through the return line 78. The intermediate concentrated water tank 68 is also provided with a flow line 80 of concentrated water that overflows. The flow line 80 reaches the treated water tank 10 through the calcium removing means 82. The calcium removing means 82 can be omitted when there is substantially no or a relatively small amount of difficult-to-tolerate salt precipitated in the concentrated water.

最下流電気透析装置８は、第一の室８４と第二の室８６とを有する極性転換方式（定期的に極性が転換されて、第一の室８４が脱イオン室として機能し第二の室８６が濃縮室として機能する状態と第一の室８４が濃縮室として機能し第二の室８６が脱イオン室として機能する状態とに定期的に転換される方式）の、それ自体は周知の電気透析装置から構成されている。図１においては、第一の室８４が脱イオン室として機能し第二の室８６が濃縮室として機能する状態が図示されている。極性転換方式の電気透析装置は、被処理水が比較的低濃度である場合にも高効率で脱イオン・濃縮処理することができ、最下流電気透析装置８として好適に選定することができる。図１に図示する状態において、最下流電気透析装置８の第一の室（脱イオン室）８４には、最下流脱イオン水槽８８、最下流脱イオン水ポンプ手段９０及び電導度計９２が付設されている。最下流脱イオン水槽８８には上記流動ライン６６を介して上記中間脱イオン水槽５６をオーバーフローする脱イオン水が供給される。最下流脱イオン水ポンプ手段９０は、最下流脱イオン水槽８８から脱イオン水を流出せしめて送給ライン９４を通して第一の室（脱イオン室）８４に送給すると共に、第一の室（脱イオン室）８４から返送ライン９６を通して最下流脱イオン水槽８８に脱イオン水を返送する。電導度計９２は返送ライン９６を流動する脱イオン水の電導度を測定する。最下流脱イオン水槽８８には脱イオン水流出ライン９８も配設されており、この脱イオン水流出ライン９８は脱イオン水受槽１００まで延びている。上記送給ライン９４には、オーバーフローする脱イオン水の流動ライン１０２が接続されている。最下流電気透析装置８の第二の室（濃縮室）８６には、最下流濃縮水槽１０４、最下流濃縮水ポンプ手段１０６、電導度計１０８及びｐＨ計１１０が付設されている。上記流動ライン１０２は最下流濃縮水槽１０４まで延びている。最下流濃縮水ポンプ手段１０６は、最下流濃縮水槽１０４から濃縮水を流出せしめて送給ライン１1２を通して第二の室（濃縮室）８６に送給すると共に、第二の室（濃縮室）８６から返送ライン１１４を通して最下流濃縮水槽１０４に濃縮水を返送する。電導度計１０８は返送ライン１１４を流動する濃縮水の電導度を計測し、ｐＨ計１１０は返送ライン１１４を流動する濃縮水のｐＨを計測する。最下流濃縮水槽１０４にはオーバーフローする濃縮水の流動ライン１１６も配設されており、この流動ライン１１６は上記中間濃縮水槽６８まで延びている。最下流電気透析装置８の極性が転換されて第一の室８４が濃縮室として機能し第二の室８６が脱イオン室として機能する状態に転換されたときには、適宜の接続転換手段（図示していない）によって接続転換が遂行され、最下流脱インオ水槽８８に配設されている送給ライン９４及び返送ライン９６が第一の室８４ではなくて第二の室８６に接続され、最下流濃縮水槽１０４に配設されている送給ライン１１２及び返送ライン１１４が第二の室８６ではなくて第一の室８４に接続される。所望ならば、最下流濃縮水槽１０４の配設を省略し、最下流脱イオン水槽８８から適宜に送給ライン１１２に脱イオン水を送給し、返送ライン１１４にオーバーフローする濃縮水の流動ラインを接続し、この流動ラインを中間濃縮水槽６８まで延ばすこともできる。 The most downstream electrodialysis apparatus 8 has a polarity switching system having a first chamber 84 and a second chamber 86 (the polarity is periodically changed so that the first chamber 84 functions as a deionization chamber, The chamber 86 is regularly switched between a state in which it functions as a concentrating chamber and a state in which the first chamber 84 functions as a concentrating chamber and the second chamber 86 functions as a deionizing chamber). The electrodialysis apparatus is comprised. FIG. 1 shows a state where the first chamber 84 functions as a deionization chamber and the second chamber 86 functions as a concentration chamber. The electrodialysis apparatus of the polarity switching system can be deionized and concentrated with high efficiency even when the water to be treated has a relatively low concentration, and can be suitably selected as the most downstream electrodialysis apparatus 8. In the state illustrated in FIG. 1, the first chamber (deionization chamber) 84 of the most downstream electrodialysis apparatus 8 is provided with a most downstream deionized water tank 88, a most downstream deionized water pump means 90, and a conductivity meter 92. Has been. The most downstream deionized water tank 88 is supplied with deionized water that overflows the intermediate deionized water tank 56 via the flow line 66. The most downstream deionized water pump means 90 discharges deionized water from the most downstream deionized water tank 88 and feeds it to the first chamber (deionized chamber) 84 through the feed line 94, while also supplying the first chamber ( The deionized water is returned from the deionized chamber 84 to the most downstream deionized water tank 88 through the return line 96. A conductivity meter 92 measures the conductivity of deionized water flowing through the return line 96. The most downstream deionized water tank 88 is also provided with a deionized water outflow line 98, and this deionized water outflow line 98 extends to the deionized water receiving tank 100. A flow line 102 of deionized water that overflows is connected to the feed line 94. The second chamber (concentration chamber) 86 of the most downstream electrodialysis apparatus 8 is provided with a most downstream concentrated water tank 104, a most downstream concentrated water pump means 106, an electric conductivity meter 108, and a pH meter 110. The flow line 102 extends to the most downstream concentrated water tank 104. The most downstream concentrated water pump means 106 discharges the concentrated water from the most downstream concentrated water tank 104 and feeds it to the second chamber (concentration chamber) 86 through the feed line 112, and also the second chamber (concentration chamber) 86. The concentrated water is returned to the most downstream concentrated water tank 104 through the return line 114. The conductivity meter 108 measures the conductivity of the concentrated water flowing through the return line 114, and the pH meter 110 measures the pH of the concentrated water flowing through the return line 114. A flow line 116 of the concentrated water that overflows is also disposed in the most downstream concentrated water tank 104, and the flow line 116 extends to the intermediate concentrated water tank 68. When the polarity of the most downstream electrodialyzer 8 is changed so that the first chamber 84 functions as a concentration chamber and the second chamber 86 functions as a deionization chamber, appropriate connection switching means (shown) The connection line 94 and return line 96 disposed in the most downstream deionized water tank 88 are connected to the second chamber 86 instead of the first chamber 84, and the most downstream The feed line 112 and the return line 114 disposed in the concentrated water tank 104 are connected to the first chamber 84 instead of the second chamber 86. If desired, the arrangement of the most downstream concentrated water tank 104 is omitted, and deionized water is appropriately fed from the most downstream deionized water tank 88 to the feed line 112, and the concentrated water flowing line overflows to the return line 114. It is also possible to connect and extend this flow line to the intermediate concentrated water tank 68.

次に、上述したとおりの電気透析システムにおける制御手段（図示していない）による作動制御様式について説明する。図２は３台の電気透析装置、即ち最上流電気透析装置４、中間電気透析装置６及び最下流電気透析装置８のいずれを作動せしめるかを設定する制御フローを示している。ステップｓ−１においては、被処理水の電導度、即ち電導度計１４が計測する電導度が第一の所定値、例えばイオン濃度で５００乃至４，０００ｐｐｍ程度、以下であるか否かが判別される。被処理水の電導度が第一の所定値より大きい場合にはステップｓ−２に進行し、中間電気透析装置６を作動せしめることが決定される。次いでステップｓ−３に進行し、被処理水の電導度が上記第一の所定値よりも大きい第二の所定値、例えばイオン濃度で４，０００乃至１５，０００ｐｐｍ程度、以下であるか否かが判別される。被処理水の電導度が第二の所定値よりも大きい場合にはステップｓ−４に進行し、最上流電気透析装置４を作動せしめることが決定される。次いで、ステップｓ−５に進行して、最下流電気透析装置８を作動せしめることが決定される。上記ステップｓ−１において被処理水の電導度が第一の所定値以下の場合にはステップｓ−５に進行する。また、上記ステップｓ−３において被処理水の電導度が第二の所定値以下の場合にもステップｓ−５に進行する。かようにして、本発明に従って構成された電気透析システムにおいては、被処理水の電導度が所定値（第一の所定値）以下の場合には最下流電気透析装置８のみが作動せしめられ、被処理水の電導度の増大に応じて下流側から上流側に向けて漸次電気透析装置の作動台数が増大せしめられる。図示の実施形態においては、被処理水の電導度が第一の所定値以下の場合には最下流電気透析装置8のみが作動せしめられ、被処理水の電導度が第一の所定値よりは大きいが第二の所定値以下の場合には最下流電気透析装置８と共に中間電気透析装置６が作動せしめられ、被処理水の電導度が第二の所定値よりも大きい場合には全ての電気透析装置、即ち最下流電気透析装置8と共に中間電気透析装置６及び最上流電気透析装置４が作動せしめられる。 Next, the operation control mode by the control means (not shown) in the electrodialysis system as described above will be described. FIG. 2 shows a control flow for setting which of the three electrodialyzers, that is, the most upstream electrodialyzer 4, the intermediate electrodialyzer 6, and the most downstream electrodialyzer 8 is operated. In step s-1, it is determined whether or not the conductivity of the water to be treated, that is, the conductivity measured by the conductivity meter 14 is a first predetermined value, for example, an ion concentration of about 500 to 4,000 ppm or less. Is done. If the conductivity of the water to be treated is greater than the first predetermined value, the process proceeds to step s-2 and it is determined that the intermediate electrodialysis apparatus 6 is to be operated. Next, the process proceeds to step s-3, and whether or not the conductivity of the water to be treated is a second predetermined value larger than the first predetermined value, for example, an ion concentration of about 4,000 to 15,000 ppm or less. Is determined. If the conductivity of the water to be treated is greater than the second predetermined value, the process proceeds to step s-4, and it is determined that the most upstream electrodialysis apparatus 4 is to be operated. Next, it is determined to proceed to step s-5 to operate the most downstream electrodialysis apparatus 8. When the conductivity of the water to be treated is not more than the first predetermined value in step s-1, the process proceeds to step s-5. Moreover, also when the electrical conductivity of to-be-processed water is below a 2nd predetermined value in said step s-3, it progresses to step s-5. Thus, in the electrodialysis system configured according to the present invention, when the conductivity of the water to be treated is equal to or lower than a predetermined value (first predetermined value), only the most downstream electrodialyzer 8 is activated, The number of operating electrodialyzers is gradually increased from the downstream side toward the upstream side as the conductivity of the water to be treated increases. In the illustrated embodiment, when the conductivity of the water to be treated is equal to or lower than the first predetermined value, only the most downstream electrodialysis apparatus 8 is activated, and the conductivity of the water to be treated is lower than the first predetermined value. If it is larger but less than the second predetermined value, the intermediate electrodialyzer 6 is operated together with the most downstream electrodialyzer 8, and if the conductivity of the water to be treated is larger than the second predetermined value, all electric The intermediate electrodialysis device 6 and the most upstream electrodialysis device 4 are operated together with the dialysis device, that is, the most downstream electrodialysis device 8.

図３を参照して最上流電気透析装置４の作動制御手順を説明すると、ステップｓ−６においては、最上流電気透析装置４を作動すべき設定がなされているか否かが判別される。最上流電気透析装置４を作動すべき設定がなされている場合にはステップｓ−７に進行し、最上流脱イオン水槽２２中の脱イオン水及び最上流濃縮水槽３４中の濃縮水が所定レベル以上か否かが判別される。最上流脱イオン水槽２２中の脱イオン水のレベル及び／又は最上流濃縮水槽３４中の濃縮水のレベルが所定レベルより低い場合にはステップｓ−８に進行し、被処理水供給ポンプ手段１２を作動せしめると共に供給ライン１６中に配設されている開閉制御弁（図示していない）を開動して最上流脱イオン水槽２２に被処理水を供給する及び／又は被処理水供給ポンプ手段１２を作動せしめると共に分岐供給ライン４２中に配設されている開閉制御弁（図示していない）を開動して最上流濃縮水槽３４に被処理水を供給する。ステップｓ−７において最上流脱イオン水槽２２中の脱イオン水のレベル及び最上流濃縮水槽３４中の濃縮水のレベルが所定レベル以上の場合にはステップｓ−９に進行する。このステップｓ−９においては、最上流脱イオン水ポンプ手段２４が作動せしめられて脱イオン室１８を通る脱イオン水の循環が開始されると共に、最上流濃縮水ポンプ手段３６が作動せしめられて濃縮室２０を通る濃縮水の循環が開始される。次いで、ステップｓ−１０において最上流電気透析装置４に作動電力が供給され、最上流電気透析装置４の作動が開始される。最上流電気透析装置４が作動される際には、ステップｓ−１１において電導度計２６が計測する脱イオン水の電導度が所定値、例えばイオン濃度で４，０００乃至１５，０００ｐｐｍ程度、以下であるか否かが判別され、脱イオン水の電導度が所定値以下の場合にはステップｓ−１２に進行し、最上流脱イオン水槽２２への被処理水の供給が開始される。また、ステップｓ−１３において電導度計３８が計測する濃縮水の電導度が所定値、例えばイオン濃度で１５，０００乃至７０，０００ｐｐｍ程度、以上か否かが判別され、濃縮水の電導度が所定値以上の場合にはステップｓ−１４に進行し、最上流濃縮水槽３４に配設されている濃縮水流出ライン４８に設けられている開閉制御弁（図示していない）が開動され、最上流濃縮水槽３４内の濃縮水が流出ライン４８を通して濃縮水受槽５０に送給される。濃縮水受槽５０に送給された濃縮水は、乾燥加熱装置に供給するのに適したイオン濃度を有し、加熱乾燥装置において高効率で加熱固化して塩を生成することができる。ステップｓ−１５においては、電導度計３８が計測する濃縮水の電導度が過大であり最上流電気透析装置４の作動効率の低減を誘発する可能性があるか否かが判別される。濃縮水の電導度が過大である場合にはステップｓ−１６に進行し、分岐供給ライン４２を通して最上流濃縮水槽３４に被処理水が送給されて濃縮水が希釈される。更に、ステップｓ−１７においては、ｐＨ計４０が測定する濃縮水のｐＨが最上流電気透析装置４の作動効率の低減を誘発する虞がある所定値（例えば１．０乃至６．０程度）以上であるか否かが判別される。そして濃縮水のｐＨが所定値以上である場合にはステップｓ−１８に進行し、適宜の供給源（図示していない）から濃縮水に塩酸が供給される。上記ステップｓ−６において最上流電気透析装置４を作動すべき設定がなされていない場合には、ステップｓ−１９に進行し、最上流電気透析装置４に電力が供給されている場合にはこれを停止し、最上流脱イオン水ポンプ手段２４及び最上流濃縮水ポンプ手段３６が作動せしめられている場合にはこれらの作動を停止する。 The operation control procedure of the most upstream electrodialysis apparatus 4 will be described with reference to FIG. 3. In step s-6, it is determined whether or not the setting for operating the most upstream electrodialysis apparatus 4 has been made. When the setting for operating the most upstream electrodialysis apparatus 4 is made, the process proceeds to step s-7, and the deionized water in the most upstream deionized water tank 22 and the concentrated water in the most upstream concentrated water tank 34 are at predetermined levels. It is determined whether or not this is the case. When the level of deionized water in the uppermost stream deionized water tank 22 and / or the level of concentrated water in the uppermost stream concentrated water tank 34 is lower than a predetermined level, the process proceeds to step s-8 and the treated water supply pump means 12 is processed. And the open / close control valve (not shown) disposed in the supply line 16 is opened to supply the treated water to the most upstream deionized water tank 22 and / or the treated water supply pump means 12. And the open / close control valve (not shown) disposed in the branch supply line 42 is opened to supply the water to be treated to the uppermost concentrated water tank 34. In step s-7, when the level of deionized water in the most upstream deionized water tank 22 and the level of concentrated water in the most upstream concentrated water tank 34 are higher than a predetermined level, the process proceeds to step s-9. In step s-9, the most upstream deionized water pump means 24 is activated to start circulation of deionized water through the deionization chamber 18, and the most upstream concentrated water pump means 36 is activated. Circulation of concentrated water through the concentration chamber 20 is started. Next, in step s-10, operating power is supplied to the most upstream electrodialysis apparatus 4, and the operation of the most upstream electrodialysis apparatus 4 is started. When the most upstream electrodialysis apparatus 4 is operated, the conductivity of deionized water measured by the conductivity meter 26 in step s-11 is a predetermined value, for example, an ion concentration of about 4,000 to 15,000 ppm or less. If the conductivity of the deionized water is equal to or lower than the predetermined value, the process proceeds to step s-12, and the supply of the treated water to the most upstream deionized water tank 22 is started. In step s-13, it is determined whether or not the conductivity of the concentrated water measured by the conductivity meter 38 is a predetermined value, for example, about 15,000 to 70,000 ppm in terms of ion concentration, and the conductivity of the concentrated water is determined. If it is equal to or greater than the predetermined value, the process proceeds to step s-14, where an open / close control valve (not shown) provided in the concentrated water outflow line 48 provided in the most upstream concentrated water tank 34 is opened. The concentrated water in the upstream concentrated water tank 34 is fed to the concentrated water receiving tank 50 through the outflow line 48. The concentrated water supplied to the concentrated water receiving tank 50 has an ion concentration suitable for supplying to the drying and heating device, and can be heated and solidified with high efficiency in the heating and drying device to generate a salt. In step s-15, it is determined whether or not the electric conductivity of the concentrated water measured by the electric conductivity meter 38 is excessive and may cause a reduction in the operating efficiency of the most upstream electrodialysis apparatus 4. If the conductivity of the concentrated water is excessive, the process proceeds to step s-16, where the water to be treated is supplied to the uppermost concentrated water tank 34 through the branch supply line 42 to dilute the concentrated water. Further, in step s-17, the pH of the concentrated water measured by the pH meter 40 is a predetermined value (for example, about 1.0 to 6.0) that may cause a reduction in the operating efficiency of the most upstream electrodialysis apparatus 4. It is determined whether or not this is the case. If the pH of the concentrated water is equal to or higher than the predetermined value, the process proceeds to step s-18, and hydrochloric acid is supplied to the concentrated water from an appropriate supply source (not shown). If it is determined in step s-6 that the most upstream electrodialyzer 4 is not set to operate, the process proceeds to step s-19, and if the most upstream electrodialyzer 4 is supplied with power, this is performed. When the most upstream deionized water pump means 24 and the most upstream concentrated water pump means 36 are operated, these operations are stopped.

図４を参照して中間電気透析装置６の作動制御手順を説明すると、ステップｓ−２０においては、中間電気透析装置６を作動すべき設定がなされているか否かが判別される。中間電気透析装置６を作動すべき設定がなされている場合にはステップｓ−２１に進行し、中間脱イオン水槽５６中の脱イオン水及び中間濃縮水槽６８中の濃縮水が所定レベル以上か否かが判別される。中間脱イオン水槽５６中の脱イオン水のレベル及び／又は中間濃縮水槽６８中の濃縮水のレベルが所定レベルより低い場合にはステップｓ−２２に進行し、被処理水供給ポンプ手段１２を作動せしめると共に供給ライン１６中に配設されている開閉制御弁（図示していない）を開動して最上流脱イオン水槽２２に被処理水を供給する。最上流脱イオン水槽２２に被処理水を供給すると、流動ライン３２を通して中間脱イオン水槽５６に被処理水が供給され、そして更に流動ライン６６、最下流イオン水槽８８、送給ライン９４、流動ライン１０２、最下流濃縮水槽１０４及び流動ライン１１６を通して中間濃縮水槽６８に被処理水が供給される。ステップｓ−２０において中間脱イオン水槽５６中の脱イオン水のレベル及び中間濃縮水槽６８中の濃縮水のレベルが所定レベル以上の場合にはステップｓ−２３に進行する。このステップｓ−２３においては、中間脱イオン水ポンプ手段５８が作動せしめられて脱イオン室５２を通る脱イオン水の循環が開始されると共に、中間濃縮水ポンプ手段７０が作動せしめられて濃縮室５４を通る濃縮水の循環が開始される。次いで、ステップｓ−２４において中間電気透析装置６に作動電力が供給され、中間電気透析装置６の作動が開始される。中間電気透析装置６が作動される際には、ステップｓ−２５において電導度計６０が計測する脱イオン水の電導度が所定値、例えばイオン濃度で５００乃至４，０００ｐｐｍ程度、以下であるか否かが判別され、脱イオン水の電導度が所定値以下の場合にはステップｓ−２６に進行し、最上流脱イオン水槽２２及び流動ライン３２を介して中間脱イオン水槽５６に被処理水が供給される。また、ステップｓ−２７においては、電導度計７２が計測する濃縮水の電導度が過大であり中間電気透析装置６の作動効率の低減を誘発する可能性があるか否かが判別される。濃縮水の電導度が過大である場合にはステップｓ−２８に進行し、最上流脱イオン水槽２２、流動ライン３２、中間脱イオン水槽５６、流動ライン６６、最下流脱イオン水槽８８、送給ライン９４、流動ライン１０２、最下流濃縮水槽１０４及び流動ライン１１６を通して中間濃縮水槽６８に被処理水が送給され、濃縮水が希釈される。更に、ステップｓ−２９においては、ｐＨ計７４が測定する濃縮水のｐＨが中間電気透析装置６の作動効率の低減を誘発する虞がある所定値（例えば１．０乃至６．０程度）以上であるか否かが判別される。そして濃縮水のｐＨが所定値以上である場合にはステップｓ−３０に進行し、適宜の供給源（図示していない）から濃縮水に塩酸が供給される。上記ステップｓ−２０において中間電気透析装置６を作動すべき設定がなされていない場合には、ステップｓ−３１に進行し、中間電気透析装置６に電力が供給されている場合にはこれを停止し、中間脱イオン水ポンプ手段５８及び中間濃縮水ポンプ手段７０が作動せしめられている場合にはこれらの作動を停止する。 The operation control procedure of the intermediate electrodialyzer 6 will be described with reference to FIG. 4. In step s-20, it is determined whether or not the setting for operating the intermediate electrodialyzer 6 has been made. When the setting for operating the intermediate electrodialyzer 6 is made, the process proceeds to step s-21, and whether or not the deionized water in the intermediate deionized water tank 56 and the concentrated water in the intermediate concentrated water tank 68 are equal to or higher than a predetermined level. Is determined. When the level of deionized water in the intermediate deionized water tank 56 and / or the level of concentrated water in the intermediate concentrated water tank 68 is lower than a predetermined level, the process proceeds to step s-22 to operate the water supply pump means 12 to be treated. At the same time, an open / close control valve (not shown) provided in the supply line 16 is opened to supply the water to be treated to the most upstream deionized water tank 22. When the water to be treated is supplied to the most upstream deionized water tank 22, the water to be treated is supplied to the intermediate deionized water tank 56 through the flow line 32, and further the flow line 66, the most downstream ion water tank 88, the supply line 94, and the flow line. The treated water is supplied to the intermediate concentrated water tank 68 through 102, the most downstream concentrated water tank 104 and the flow line 116. When the level of deionized water in the intermediate deionized water tank 56 and the level of concentrated water in the intermediate concentrated water tank 68 are equal to or higher than the predetermined level in step s-20, the process proceeds to step s-23. In this step s-23, the intermediate deionized water pump means 58 is actuated to start circulation of deionized water through the deionization chamber 52, and the intermediate concentrated water pump means 70 is actuated to activate the concentration chamber. Concentrated water circulation through 54 is started. Next, in step s-24, operating electric power is supplied to the intermediate electrodialysis apparatus 6, and the operation of the intermediate electrodialysis apparatus 6 is started. When the intermediate electrodialysis apparatus 6 is operated, is the conductivity of deionized water measured by the conductivity meter 60 in step s-25 a predetermined value, for example, an ion concentration of about 500 to 4,000 ppm or less? If the conductivity of the deionized water is equal to or lower than the predetermined value, the process proceeds to step s-26, and the water to be treated is transferred to the intermediate deionized water tank 56 via the most upstream deionized water tank 22 and the flow line 32. Is supplied. Further, in step s-27, it is determined whether or not the conductivity of the concentrated water measured by the conductivity meter 72 is excessive and may cause a reduction in the operating efficiency of the intermediate electrodialysis apparatus 6. When the conductivity of the concentrated water is excessive, the process proceeds to step s-28, and the most upstream deionized water tank 22, the flow line 32, the intermediate deionized water tank 56, the flow line 66, the most downstream deionized water tank 88, and the feed The treated water is fed to the intermediate concentrated water tank 68 through the line 94, the flow line 102, the most downstream concentrated water tank 104 and the flow line 116, and the concentrated water is diluted. Further, in step s-29, the pH of the concentrated water measured by the pH meter 74 is not less than a predetermined value (for example, about 1.0 to 6.0) that may induce a reduction in the operating efficiency of the intermediate electrodialysis apparatus 6. It is determined whether or not. If the pH of the concentrated water is equal to or higher than the predetermined value, the process proceeds to step s-30, and hydrochloric acid is supplied to the concentrated water from an appropriate supply source (not shown). If it is determined in step s-20 that the intermediate electrodialysis apparatus 6 is not set to operate, the process proceeds to step s-31, and if power is supplied to the intermediate electrodialysis apparatus 6, this is stopped. When the intermediate deionized water pump means 58 and the intermediate concentrated water pump means 70 are operated, these operations are stopped.

次に、図５を参照して最下流電気透析装置８の作動制御手順を説明する。ステップｓ−３２においては最下流脱イオン水槽８８中の脱イオン水及び最下流濃縮水槽１０４中の濃縮水が所定レベル以上か否かが判別される。最下流脱イオン水槽８８中の脱イオン水のレベル及び／又は最下流濃縮水槽１０４中の濃縮水のレベルが所定レベルより低い場合にはステップｓ−３３に進行し、被処理水供給ポンプ手段１２を作動せしめると共に供給ライン１６中に配設されている開閉制御弁（図示していない）を開動して最上流脱イオン水槽２２に被処理水を供給する。最上流脱イオン水槽２２に被処理水を供給すると、流動ライン３２、中間脱イオン水槽５６及び流動ライン６６を通して最下流脱イオン水槽８８に非処理水が供給され、そして更に送給ライン９４、流動ライン１０２を介して最下流濃縮水槽１０４に被処理水が供給される。ステップｓ−３２において最下流脱イオン水槽８８中の脱イオン水のレベル及び最下流濃縮水槽１０４中の濃縮水のレベルが所定レベル以上の場合にはステップｓ−３４に進行する。このステップｓ−３４においては、最下流脱イオン水ポンプ手段９０が作動せしめられて脱イオン室８４を通る脱イオン水の循環が開始されると共に、最下流濃縮水ポンプ手段１０６が作動せしめられて濃縮室８６を通る濃縮水の循環が開始される。次いで、ステップｓ−３５において最下流電気透析装置８に作動電力が供給され、最下流電気透析装置８の作動が開始される。次いで、ステップｓ−３６に進行し、最下流電気透析装置８の作動を開始から所定時間、例えば１５分乃至１２時間程度、以上経過したか否かが判別される。所定時間以上経過した場合にはステップｓ−３７に進行し、最下流電気透析装置８の極性が転換されると共に極性転換に付随して必要な上記接続転換操作が遂行される。一方、ステップｓ−３８においては、電導度計９２が測定する電導度が所定値、例えばイオン濃度で１００乃至１,０００ｐｐｍ程度、以下であるか否かが判別される。電導度が所定値以下である場合にはステップｓ−３９に進行し、このステップｓ−３９においては脱イオン水流出ライン９８に配設されている開閉制御弁（図示していない）が開動され、最下流脱イオン水槽８８からイオン濃度が充分に低減せしめられた脱イオン水が脱イオン水受槽１００に流出せしめられる。脱イオン水槽１００に流出せしめられた脱イオン水は、イオン濃度が充分に低減されている故に、例えば農業用水として利用し或いは河川に放流することができる。更に、最下流電気透析装置８が作動される際には、ステップｓ−４０において、電導度計１０８が計測する濃縮水の電導度が過大であり最下流電気透析装置８の作動効率の低減を誘発する可能性があるか否かが判別される。濃縮水の電導度が過大である場合にはステップｓ−４１に進行し、最上流脱イオン水槽２２、流動ライン３２、中間脱イオン水槽５６、流動ライン６６、最下流脱イオン水槽８８、送給ライン９４及び流動ライン１０２を通して最下流濃縮水槽１０４に被処理水が送給され、濃縮水が希釈される。また、ステップｓ−４２においては、ｐＨ計１１０が測定する濃縮水のｐＨが最下流電気透析装置８の作動効率の低減を誘発する虞がある所定値（例えば１．０乃至６．０程度）以上であるか否かが判別される。そして濃縮水のｐＨが所定値以上である場合にはステップｓ−４３に進行し、適宜の供給源（図示していない）から濃縮水に塩酸が供給される。 Next, the operation control procedure of the most downstream electrodialysis apparatus 8 will be described with reference to FIG. In step s-32, it is determined whether or not the deionized water in the most downstream deionized water tank 88 and the concentrated water in the most downstream concentrated water tank 104 are above a predetermined level. When the level of deionized water in the most downstream deionized water tank 88 and / or the level of concentrated water in the most downstream concentrated water tank 104 is lower than a predetermined level, the process proceeds to step s-33, and the treated water supply pump means 12 And the open / close control valve (not shown) disposed in the supply line 16 is opened to supply the treated water to the most upstream deionized water tank 22. When treated water is supplied to the most upstream deionized water tank 22, untreated water is supplied to the most downstream deionized water tank 88 through the flow line 32, the intermediate deionized water tank 56 and the flow line 66, and further, the supply line 94, flow The treated water is supplied to the most downstream concentrated water tank 104 via the line 102. In step s-32, when the level of deionized water in the most downstream deionized water tank 88 and the level of concentrated water in the most downstream concentrated water tank 104 are higher than a predetermined level, the process proceeds to step s-34. In this step s-34, the most downstream deionized water pump means 90 is activated to start circulation of deionized water through the deionization chamber 84, and the most downstream concentrated water pump means 106 is activated. Circulation of concentrated water through the concentration chamber 86 is started. Next, in step s-35, operating power is supplied to the most downstream electrodialysis apparatus 8, and the operation of the most downstream electrodialysis apparatus 8 is started. Next, the process proceeds to step s-36, and it is determined whether or not a predetermined time, for example, about 15 minutes to 12 hours has elapsed since the start of the operation of the most downstream electrodialyzer 8. When the predetermined time or more has elapsed, the process proceeds to step s-37, where the polarity of the most downstream electrodialysis apparatus 8 is changed and the necessary connection changing operation accompanying the polarity change is performed. On the other hand, in step s-38, it is determined whether or not the conductivity measured by the conductivity meter 92 is a predetermined value, for example, an ion concentration of about 100 to 1,000 ppm or less. When the electrical conductivity is less than or equal to the predetermined value, the process proceeds to step s-39, and in this step s-39, an open / close control valve (not shown) disposed in the deionized water outflow line 98 is opened. The deionized water in which the ion concentration is sufficiently reduced is discharged from the most downstream deionized water tank 88 to the deionized water receiving tank 100. Since the ion concentration is sufficiently reduced, the deionized water that has flowed into the deionized water tank 100 can be used, for example, as agricultural water or discharged into a river. Further, when the most downstream electrodialysis apparatus 8 is operated, in step s-40, the conductivity of the concentrated water measured by the conductivity meter 108 is excessive, and the operation efficiency of the most downstream electrodialysis apparatus 8 is reduced. It is determined whether there is a possibility of triggering. When the conductivity of the concentrated water is excessive, the process proceeds to step s-41, and the most upstream deionized water tank 22, the flow line 32, the intermediate deionized water tank 56, the flow line 66, the most downstream deionized water tank 88, and the feed The treated water is fed to the most downstream concentrated water tank 104 through the line 94 and the flow line 102, and the concentrated water is diluted. In step s-42, the pH of the concentrated water measured by the pH meter 110 may induce a reduction in the operating efficiency of the most downstream electrodialysis apparatus 8 (for example, about 1.0 to 6.0). It is determined whether or not this is the case. If the pH of the concentrated water is equal to or higher than the predetermined value, the process proceeds to step s-43, and hydrochloric acid is supplied to the concentrated water from an appropriate supply source (not shown).

２：被処理水供給手段
４：最上流電気透析装置
６：中間電気透析装置
８：最下流電気透析装置
１０：被処理水タンク
１４：電導度計
２２：最上流脱イオン水槽
２４：最上流脱イオン水ポンプ手段
２６：電導度計
３４：最上流濃縮水槽
３６：最上流濃縮水ポンプ手段
３８：電導度計
５０：濃縮水受槽
５６：中間脱イオン水槽
５８：中間脱イオン水ポンプ手段
６０：電導度計
６８：中間濃縮水槽
７０：中間濃縮水ポンプ手段
７２：電導度計
８８：最下流脱イオン水槽
９０：最下流脱イオン水ポンプ手段
９２：電導度計
１００：脱イオン水受槽
１０４：最下流濃縮水槽
１０６：最下流濃縮水ポンプ手段
１０８：電導度計 2: treated water supply means 4: most upstream electrodialysis device 6: intermediate electrodialysis device 8: most downstream electrodialysis device 10: treated water tank 14: conductivity meter 22: most upstream deionized water tank 24: most upstream dewatering Ionized water pump means 26: Conductivity meter 34: Most upstream concentrated water tank 36: Most upstream concentrated water pump means 38: Conductivity meter 50: Concentrated water receiving tank 56: Intermediate deionized water tank 58: Intermediate deionized water pump means 60: Electrical conduction Meter 68: Intermediate concentrated water tank 70: Intermediate concentrated water pump means 72: Conductivity meter 88: Most downstream deionized water tank 90: Most downstream deionized water pump means 92: Conductivity meter 100: Deionized water receiving tank 104: Most downstream Concentrated water tank 106: Downstream concentrated water pump means 108: Conductivity meter

Claims

Along with at least two electrodialyzers arranged in series, a treated water supply means and a control means for supplying the treated water to be deionized and concentrated,
The treated water supply means supplies treated water to the most upstream deionized water tank attached to the most upstream electrodialysis apparatus located at the most upstream, and concentrates from the most upstream concentrated water tank attached to the most upstream electrodialysis apparatus. Water was allowed to flow out, and deionized water was allowed to flow out from the deionized water tank attached to the most downstream electrodialysis apparatus located at the most downstream,
The control means sets the number of electrodialyzers to be activated according to the conductivity of the water to be treated.
An electrodialysis system characterized by that.

The control means activates only the most downstream electrodialyzer when the conductivity of the water to be treated is a predetermined value or less, and moves from the downstream side to the upstream side according to the increase in the conductivity of the water to be treated. The electrodialysis system according to claim 1, wherein the number of operating electrodialyzers is gradually increased.

The electrodialysis system according to claim 1 or 2, wherein the most downstream electrodialysis apparatus is a polarity conversion system, and the other electrodialysis apparatus is a nonpolar conversion system.

Concentrated water discharged from the concentrated water tank attached to the most upstream electrodialysis apparatus has an ion concentration of a predetermined high concentration or more, and deionized water discharged from the most downstream electrodialysis apparatus has a predetermined low concentration or less. The electrodialysis system according to any one of claims 1 to 3, which has an ion concentration.

In addition to the most upstream electrodialysis device and the most downstream electrodialysis device, including at least one intermediate electrodialysis device located between the most upstream electrodialysis device and the most downstream electrodialysis device,
The most upstream electrodialysis apparatus supplies deionized water in the most upstream deionized water tank to the deionization chamber of the most upstream electrodialysis apparatus and deionized water deionized in the most upstream electrodialysis apparatus. The most upstream deionized water pump means for returning the concentrated water in the most upstream deionized water tank, and the concentrated water in the most upstream concentrated water tank is fed to the concentrating chamber of the most upstream electrodialysis apparatus and the most upstream electrodialysis An uppermost stream concentrated water pump means for returning the concentrated water concentrated in the apparatus to the uppermost stream concentrated water tank;
In the intermediate electrodialysis apparatus, an intermediate deionized water tank, an intermediate concentrated water tank, and deionized water in the intermediate deionized water tank are supplied to the deionization chamber of the intermediate electrodialysis apparatus and in the intermediate electrodialysis apparatus Intermediate deionized water pump means for returning deionized deionized water to the intermediate deionized water tank, and the concentrated water in the intermediate concentrated water tank are fed to the concentration chamber of the intermediate electrodialyzer and the intermediate An intermediate concentrated water pump means for returning the concentrated water concentrated in the electrodialyzer to the intermediate concentrated water tank is attached,
The most downstream electrodialyzer supplies the most downstream deionized water tank, the most downstream concentrated water tank, and the deionized water in the most downstream deionized water tank to the deionized chamber of the most downstream electrodialyzer and The most downstream deionized water pump means for returning deionized water deionized in the most downstream electrodialyzer to the most downstream deionized water tank, and the concentrated water in the most downstream concentrated water tank is used as the most downstream electrodialyzer. And the most downstream concentrated water pump means for returning the concentrated water concentrated in the most downstream electrodialyzer to the most downstream concentrated water tank,
The deionized water that has overflowed the most upstream deionized water tank is caused to flow into the intermediate deionized water tank, and the deionized water that has overflowed the intermediate deionized water tank is caused to flow into the most downstream deionized water tank, and the most downstream The deionized water overflowed from the deionized water circulation path circulated through the deionization chamber of the electrodialyzer is caused to flow into the most downstream concentrated water tank,
The concentrated water overflowing the most downstream concentrated water tank is caused to flow into the intermediate concentrated water tank, and the concentrated water overflowing from the intermediate concentrated water tank is returned to the treated water supply means.
The electrodialysis system according to any one of claims 1 to 4.

The electrodialysis system according to claim 5, wherein the concentrated water overflowed from the intermediate concentrated water tank is supplied to the calcium removing means and subjected to the calcium removing treatment before being returned to the treated water supply means.