JPH10137542A - Treatment of flue gas desulfurization waste water - Google Patents
Treatment of flue gas desulfurization waste waterInfo
- Publication number
- JPH10137542A JPH10137542A JP8322197A JP32219796A JPH10137542A JP H10137542 A JPH10137542 A JP H10137542A JP 8322197 A JP8322197 A JP 8322197A JP 32219796 A JP32219796 A JP 32219796A JP H10137542 A JPH10137542 A JP H10137542A
- Authority
- JP
- Japan
- Prior art keywords
- membrane
- cleaning
- gas desulfurization
- flue gas
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Treating Waste Gases (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、排煙脱硫排水の処
理方法に関する。さらに詳しくは、本発明は、石炭火力
発電所の排煙脱硫排水の、膜を用いた固液分離濃縮工程
を伴う処理において、洗浄による膜性能の回復率に優
れ、膜の交換頻度を低減することができる排煙脱硫排水
の処理方法、及び、さらに洗浄によって発生した洗浄廃
液自体の処理を省くことができる排煙脱硫排水の処理方
法に関する。[0001] The present invention relates to a method for treating flue gas desulfurization wastewater. More specifically, the present invention has an excellent recovery rate of membrane performance by washing, and reduces the frequency of membrane replacement, in a process involving a solid-liquid separation / concentration step using a membrane, of a flue gas desulfurization effluent of a coal-fired power plant. The present invention relates to a method for treating flue gas desulfurization effluent, and a method for treating flue gas desulfurization effluent that can eliminate the treatment of the cleaning waste liquid itself generated by washing.
【０００２】[0002]
【従来の技術】排煙脱硫排水は、石油、石炭等の燃料を
燃焼した際に発生する排煙を、洗煙、脱硫処理したとき
に生ずる排水であり、硫酸イオン、亜硫酸イオン、カル
シウムイオン等のイオン類や石膏等の懸濁物、燃料に由
来するＣＯＤ成分のほか、鉄、アルミニウム、マンガ
ン、その他重金属等の金属や、ふっ素、シリカ等を含有
している。このような汚染物質を含む排煙脱硫排水を処
理するときは、先ず排水中の汚染物質を凝集処理してで
きるだけ固形分として水中から分離する。固形化せず水
中に溶解したままの一部のＣＯＤ成分や、除去対象とな
るイオンは、吸着工程、イオン除去工程、分解処理工程
等により除去する。また、ＣＯＤの対象となる還元性物
質、例えば、亜硫酸イオン、マンガンイオン等を除去す
るために、酸化工程が設けられる。酸化工程、凝集工程
を経た排水は、凝集によって生成したフロックを膜によ
って分離する。膜分離工程で使用する膜は、処理の継続
により膜面が汚染され透過水量（フラックス）が低下す
る。このため、透過水量が低下したときは、透過水側か
ら処理水を逆流させる逆流洗浄や、洗浄剤を含む液で膜
を洗う薬液洗浄が行われる。従来、一般的な薬液洗浄
は、通常、アルカリ液や酸液が用いられたり、これらの
液を併用して行われている。ポリ塩化アルミ（ＰＡ
Ｃ）、硫酸バンド、水酸化マグネシウム、塩化第二鉄、
消石灰等を排液の凝集中和に用いた場合、濃縮時に発生
する懸濁物質（ＳＳ）はアルカリ又は鉱酸による溶解が
可能である。そのため従来は、膜の薬品洗浄は水酸化ナ
トリウム等のアルカリや、塩酸等の鉱酸を用いて行われ
ていた。水酸化ナトリウムはシリカを溶解するために４
０〜６０℃に加温し、鉱酸はその他の金属類を溶解する
ために常温又は加温し膜に接触させる。しかし、排煙脱
硫排水に適用した膜に対しては、アルカリや酸による洗
浄効果は十分でなく、通液一定期間ごとに、通常しばし
ば用いられる水酸化ナトリウムや塩酸、硫酸による洗浄
を繰り返すと洗浄回復率が十分でなく、徐々に膜性能が
低下し、膜の交換頻度が高くなるという問題点があっ
た。また、通常運転時のフラックス低下速度も早く、薬
品洗浄実施の期間も早くなり、装置稼働率の低下、洗浄
用薬品量が増大するという問題点もある。さらに薬品洗
浄を実施すると洗浄廃液が生成し、洗浄廃液を別途処理
する必要が生じ、設備費、薬剤費がかかる等の問題があ
った。2. Description of the Related Art Flue gas desulfurization waste water is waste water generated when smoke and desulfurization treatment is performed on the flue gas generated when burning fuel such as petroleum, coal, etc., such as sulfate ions, sulfite ions, and calcium ions. It contains iron, aluminum, manganese, other metals such as heavy metals, fluorine, silica, etc., in addition to COD components derived from fuel, such as suspended substances such as ions and gypsum. When treating flue gas desulfurization wastewater containing such pollutants, first, the pollutants in the wastewater are subjected to coagulation treatment and separated from the water as much as possible as solids. Some of the COD components which are not solidified but remain dissolved in water and ions to be removed are removed by an adsorption step, an ion removal step, a decomposition treatment step and the like. In addition, an oxidation step is provided to remove reducing substances to be subjected to COD, such as sulfite ions and manganese ions. The wastewater that has passed through the oxidation step and the aggregation step separates flocs generated by the aggregation by means of a membrane. The surface of the membrane used in the membrane separation step is contaminated by continuation of the treatment, and the amount of permeated water (flux) decreases. For this reason, when the amount of permeated water decreases, backwashing in which treated water flows backward from the permeated water side, or chemical cleaning in which the membrane is washed with a liquid containing a cleaning agent is performed. 2. Description of the Related Art Conventionally, general chemical cleaning is usually performed using an alkali solution or an acid solution, or by using these solutions together. Polychlorinated aluminum (PA
C), sulfate band, magnesium hydroxide, ferric chloride,
When slaked lime or the like is used for the coagulation neutralization of the waste liquid, the suspended substance (SS) generated at the time of concentration can be dissolved by an alkali or a mineral acid. Therefore, conventionally, chemical cleaning of the film has been performed using an alkali such as sodium hydroxide or a mineral acid such as hydrochloric acid. Sodium hydroxide is used to dissolve silica.
The mixture is heated to 0 to 60 ° C., and the mineral acid is brought into contact with the membrane at room temperature or with heat to dissolve other metals. However, membranes applied to flue gas desulfurization effluent do not have sufficient cleaning effects with alkalis and acids, and are washed repeatedly with sodium hydroxide, hydrochloric acid, and sulfuric acid, which are often used, at regular intervals. There is a problem that the recovery rate is not sufficient, the membrane performance gradually decreases, and the frequency of replacing the membrane increases. Further, there is also a problem that the flux lowering speed during the normal operation is faster, the period for performing the chemical cleaning is also earlier, the operation rate of the apparatus is reduced, and the amount of the cleaning chemicals is increased. Further, when the chemical cleaning is performed, a cleaning waste liquid is generated, and it is necessary to separately treat the cleaning waste liquid, and there is a problem that equipment costs and chemical costs are required.
【０００３】[0003]
【発明が解決しようとする課題】本発明は、排煙脱硫排
水を酸化、凝集、膜分離により処理する際に、膜の洗浄
回復率を高め、薬品洗浄実施の期間を延長して、膜の交
換頻度を少なくすることができ、さらに膜の洗浄廃液を
容易に処理することができる排煙脱硫排水の処理方法を
提供することを目的としてなされたものである。DISCLOSURE OF THE INVENTION The present invention is to improve the cleaning recovery rate of a membrane and extend the period of chemical cleaning when treating flue gas desulfurization wastewater by oxidation, coagulation, and membrane separation. An object of the present invention is to provide a method for treating flue gas desulfurization wastewater, which can reduce the frequency of replacement and can easily treat wastewater from washing the membrane.
【０００４】[0004]
【課題を解決するための手段】本発明者らは、上記の課
題を解決すべく鋭意研究を重ねた結果、排煙脱硫排水を
酸化、凝集、膜分離した際の膜面の汚染において、膜の
性能回復に大きな影響を与えている汚染成分が二酸化マ
ンガンであることを解明し、膜面に沈着した二酸化マン
ガンは、シュウ酸を含む洗浄液で洗浄することにより除
去することができ、さらに洗浄に用いたシュウ酸を含む
洗浄廃液は、返送して排煙脱硫排水に混合することによ
り容易に処理することができることを見いだし、この知
見に基づいて本発明を完成するに至った。すなわち、本
発明は、（１）排煙脱硫排水を、酸化工程、凝集工程、
膜分離工程に通水して処理する排煙脱硫排水の処理方法
において、処理の継続によって汚染した膜をシュウ酸を
含む洗浄液で洗浄することを特徴とする排煙脱硫排水の
処理方法、及び、（２）汚染した膜をシュウ酸を含む洗
浄液で洗浄することにより発生した洗浄廃液を、返送し
て排煙脱硫排水に混合する第(１)項記載の排煙脱硫排水
の処理方法、を提供するものである。さらに、本発明の
好ましい態様として、（３）膜分離工程において、精密
ろ過膜（ＭＦ膜）を使用する第(１)項又は第(２)項記載
の排煙脱硫排水の処理方法、（４）シュウ酸を含む洗浄
液が、濃度１〜１０重量％のシュウ酸水溶液である第
(１)〜(３)項記載の排煙脱硫排水の処理方法、（５）シ
ュウ酸を含む洗浄液が、シュウ酸０.０５〜１重量％と
鉱酸３〜１５重量％を含む混合水溶液である第(１)〜
(３)項記載の排煙脱硫排水の処理方法、（６）濃度０.
０５〜１重量％のシュウ酸水溶液と濃度３〜１５重量％
の鉱酸水溶液を併用して洗浄する第(１)〜(３)項記載の
排煙脱硫排水の処理方法、（７）汚染した膜とシュウ酸
を含む洗浄液を、常温〜８０℃において、１〜数１０時
間接触せしめる第(１)〜(６)項記載の排煙脱硫排水の処
理方法、及び、（８）汚染した膜をさらにアルカリで洗
浄する第(１)〜(７)項記載の排煙脱硫排水の処理方法、
を挙げることができる。Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that, when the flue gas desulfurization effluent is oxidized, coagulated and separated into membranes, the membrane surface is contaminated. Manganese dioxide is a contaminant that has a major effect on the performance recovery of manganese, and the manganese dioxide deposited on the film surface can be removed by washing with a cleaning solution containing oxalic acid. It has been found that the used washing waste liquid containing oxalic acid can be easily treated by being returned and mixed with flue gas desulfurization wastewater, and based on this finding, the present invention has been completed. That is, the present invention provides (1) an exhaust gas desulfurization effluent, an oxidation process, a coagulation process,
In a method for treating flue gas desulfurization wastewater that is treated by passing water through a membrane separation step, a method for treating flue gas desulfurization wastewater characterized by washing a membrane contaminated by continuation of treatment with a cleaning solution containing oxalic acid, and (2) The method for treating flue gas desulfurization effluent according to (1), wherein the washing waste liquid generated by washing the contaminated membrane with a cleaning solution containing oxalic acid is returned and mixed with the flue gas desulfurization wastewater. Is what you do. Further, as a preferred embodiment of the present invention, (3) the method for treating flue gas desulfurization effluent according to (1) or (2), wherein a microfiltration membrane (MF membrane) is used in the membrane separation step; ) The cleaning solution containing oxalic acid is an oxalic acid aqueous solution having a concentration of 1 to 10% by weight.
(1) The method for treating flue gas desulfurization effluent described in (1) to (3), (5) The cleaning solution containing oxalic acid is a mixed aqueous solution containing 0.05 to 1% by weight of oxalic acid and 3 to 15% by weight of mineral acid. Certain (1)-
(3) The method for treating flue gas desulfurization effluent described in item (3),
Oxalic acid aqueous solution of 0.5 to 1% by weight and concentration of 3 to 15% by weight
(1) The method for treating flue gas desulfurization effluent described in (1) to (3), wherein the cleaning solution containing the contaminated membrane and oxalic acid is washed at room temperature to 80 ° C. The method for treating flue gas desulfurization effluent according to the items (1) to (6), which is contacted for up to several tens of hours, and (8) The method according to the items (1) to (7), wherein the contaminated membrane is further washed with an alkali. Treatment method of flue gas desulfurization wastewater,
Can be mentioned.
【０００５】[0005]
【発明の実施の形態】本発明方法は、火力発電所等の排
煙脱硫装置から排出される排煙脱硫排水を、酸化工程、
凝集工程、膜分離工程に通水して処理する工程に適用す
ることができる。図１は、本発明の排煙脱硫排水の処理
方法の一態様の工程系統図である。本発明方法におい
て、酸化工程１は、排煙脱硫排水中に含まれているマン
ガンイオンを酸化し、不溶性の二酸化マンガンを形成す
ることを主たる目的とする。酸化の手段には特に制限は
なく、例えば、空気曝気、あるいは、過マンガン酸塩、
オゾン、塩素系酸化剤等の添加により行うことができ
る。図１においては、酸化工程が凝集反応槽２の前に設
けられているが、凝集反応槽に酸化剤を添加し、酸化工
程と凝集工程を同時に行うことも可能である。また、マ
ンガンイオンの除去とは関係なく、例えば、排水中の亜
硫酸イオンを酸化するために空気曝気する工程を含む場
合も、結果的に二酸化マンガンが生成する。また、凝集
工程において撹拌のため空気撹拌する場合にも、同様に
二酸化マンガンが生成する。本発明における酸化工程
は、上述のような二酸化マンガン除去を目的としていな
い酸化工程であってもよい。本発明方法において、酸化
工程を終了した被処理水は、凝集反応槽２へ送られる。
凝集反応槽における凝集工程において、被処理水にpH調
整剤、凝集剤等を添加して、被処理水中の懸濁物、フッ
素イオン、金属イオン、ＣＯＤ成分の一部等を凝集せし
める。凝集反応槽には、pH計３を備えることが好まし
い。pH調整剤の添加により、被処理水中の懸濁物の凝集
に適するpHとし、あるいは被処理水中に溶存するイオン
が不溶化するpHとすることができる。使用するpH調整剤
には特に制限はなく、例えば、水酸化ナトリウム、消石
灰等のアルカリや、塩酸、硫酸等の酸を使用することが
できる。使用する凝集剤には特に制限はなく、例えば、
硫酸アルミニウム、ポリ塩化アルミニウム、酸化アルミ
ニウム等のアルミニウム化合物、塩化鉄、硫酸鉄、ポリ
鉄等の鉄塩、消石灰、水酸化マグネシウム等の水酸化
物、ポリアクリルアミド、その加水分解物、カチオン変
性物、ポリアクリル酸等の高分子凝集剤等を、懸濁物の
性状に応じて適宜選択して使用することができる。凝集
剤の添加量は、被処理水中の除去対象物の量及び性状に
応じて設定することができる。BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention comprises the steps of oxidizing a flue gas desulfurization effluent discharged from a flue gas
The present invention can be applied to a process in which water is passed through a coagulation process and a membrane separation process. FIG. 1 is a process flow chart of one embodiment of the method for treating flue gas desulfurization wastewater of the present invention. In the method of the present invention, the main purpose of the oxidation step 1 is to oxidize manganese ions contained in flue gas desulfurization effluent to form insoluble manganese dioxide. The means of oxidation is not particularly limited, for example, air aeration, or permanganate,
It can be performed by adding ozone, chlorine-based oxidizing agent, or the like. In FIG. 1, the oxidation step is provided before the agglutination reaction tank 2, but it is also possible to add an oxidizing agent to the agglutination reaction tank and perform the oxidation step and the agglomeration step at the same time. Regardless of the removal of manganese ions, manganese dioxide is also generated as a result, for example, when a step of aerating air to oxidize sulfite ions in wastewater is included. Also, when air is stirred for stirring in the aggregation step, manganese dioxide is similarly generated. The oxidation step in the present invention may be an oxidation step not for the purpose of removing manganese dioxide as described above. In the method of the present invention, the water to be treated after the oxidation step is sent to the flocculation reaction tank 2.
In the coagulation step in the coagulation reaction tank, a pH adjuster, a coagulant, and the like are added to the water to be treated to aggregate a part of the suspension, fluorine ions, metal ions, and COD components in the water to be treated. The agglutination reaction tank is preferably provided with a pH meter 3. By adding a pH adjuster, a pH suitable for coagulation of a suspension in the water to be treated or a pH at which ions dissolved in the water to be treated become insoluble can be obtained. There is no particular limitation on the pH adjuster used, and for example, alkalis such as sodium hydroxide and slaked lime, and acids such as hydrochloric acid and sulfuric acid can be used. There is no particular limitation on the flocculant used, for example,
Aluminum compounds such as aluminum sulfate, polyaluminum chloride, and aluminum oxide; iron salts such as iron chloride, iron sulfate, and polyiron; hydroxides such as slaked lime and magnesium hydroxide; polyacrylamide; A polymer flocculant such as polyacrylic acid can be appropriately selected and used depending on the properties of the suspension. The addition amount of the flocculant can be set according to the amount and properties of the object to be removed in the water to be treated.
【０００６】本発明方法において、反応凝集槽において
凝集工程を終了した被処理水は、循環槽４に送られる。
循環槽中の被処理水は、循環ポンプ５を用いて膜分離装
置６に送液し、膜分離により凝集工程で生成した凝集フ
ロックを水から分離する。使用する分離膜には特に制限
はなく、例えば、精密ろ過膜（ＭＦ膜）、限外ろ過膜
（ＵＦ膜）、逆浸透膜（ＲＯ膜）、ナノフィルター膜
（ＮＦ膜）等を凝集フロックの性状に応じて適宜選択し
て使用することができるが、多くの場合、精密ろ過膜及
び限外ろ過膜を好適に使用することができる。膜エレメ
ントの形式には特に制限はなく、例えば、平面膜締め付
け型、平面膜スパイラル巻型、管状膜、中空糸膜等を使
用することができる。膜分離装置の形式にも特に制限は
なく、例えば、外圧式、内圧式あるいは加圧式、減圧式
等を適宜選択して使用することができる。循環槽より循
環ポンプにより膜モジュールに送液され、膜を透過した
水は処理水として、そのまま又はいったん処理水槽７に
入れてさらにpH調整等必要な処理を施した上で排出され
る。膜モジュールにおいて濃縮された被処理水は、一部
は凝集反応槽へ、残部は循環槽へ循環される。凝集反応
槽へ濃縮された被処理水を循環することにより、返送さ
れた汚泥が凝集反応の種晶となり、大きい、分離性のよ
いフロックを形成するので好ましい。循環槽へ循環され
た被処理水は、再度膜モジュールへ供給され、膜による
固液分離が繰り返される。膜分離により、通常、数十な
いし数百mg／リットルのＳＳを含む凝集反応槽中の被処
理水は、循環槽内の汚泥のＳＳ成分が約２重量％程度に
なるまで濃縮され、膜を透過した処理水中のＳＳは１mg
／リットル以下となる。In the method of the present invention, the water to be treated after the coagulation step in the reaction coagulation tank is sent to the circulation tank 4.
The water to be treated in the circulation tank is sent to the membrane separation device 6 using the circulation pump 5, and the flocculated floc generated in the flocculation step by the membrane separation is separated from the water. The separation membrane to be used is not particularly limited. For example, a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), a reverse osmosis membrane (RO membrane), a nanofilter membrane (NF membrane), etc. Although it can be appropriately selected and used according to the properties, in many cases, a microfiltration membrane and an ultrafiltration membrane can be suitably used. The type of the membrane element is not particularly limited, and for example, a flat membrane fastening type, a flat membrane spiral winding type, a tubular membrane, a hollow fiber membrane, or the like can be used. The type of the membrane separation device is not particularly limited, and for example, an external pressure type, an internal pressure type, a pressurized type, a depressurized type, or the like can be appropriately selected and used. The water that has been sent from the circulation tank to the membrane module by the circulation pump and permeated through the membrane is discharged as it is, as it is, or once into the treatment water tank 7 where necessary treatment such as pH adjustment is further performed. Part of the water to be treated concentrated in the membrane module is circulated to the coagulation reaction tank, and the remainder is circulated to the circulation tank. By circulating the concentrated water to be treated to the flocculation reaction tank, the returned sludge becomes a seed crystal for the flocculation reaction, and is preferable because it forms large flocs with good separability. The water to be treated circulated to the circulation tank is again supplied to the membrane module, and solid-liquid separation by the membrane is repeated. By the membrane separation, the water to be treated in the flocculation reaction tank usually containing several tens to several hundreds mg / liter of SS is concentrated until the SS component of the sludge in the circulation tank becomes about 2% by weight. SS in permeated treated water is 1mg
/ Liter or less.
【０００７】本発明方法においては、膜の使用により膜
が汚染し、透過水量が低下したとき、膜の洗浄を行う。
膜の洗浄は、逆流洗浄及び薬品洗浄によって行う。逆流
洗浄は、通常、５分ないし５時間に１回程度行うのが適
当であり、例えば、コンプレッサー８から処理水槽７に
加圧空気を送り、処理水を加圧して膜の透過側から原水
側に向かって供給し、逆流洗浄を行うことができる。逆
流洗浄では膜面の汚れを完全に除去することができず、
徐々に透過水量が減少するので薬品洗浄を行う。本発明
方法においては、シュウ酸を含む洗浄液で薬品洗浄を行
う。シュウ酸を含む洗浄液による薬品洗浄の方法には特
に制限はなく、例えば、濃度１〜１０重量％のシュウ酸
水溶液を用いて洗浄することができ、濃度０.０５〜１
重量％のシュウ酸水溶液と濃度３〜１５重量％の鉱酸水
溶液を併用して洗浄することができ、あるいは、シュウ
酸０.０５〜１重量％と鉱酸３〜１５重量％を含む混合
水溶液を用いて洗浄することができる。シュウ酸水溶液
と鉱酸水溶液を併用する場合、洗浄の順序には制限はな
く、シュウ酸水溶液で洗浄したのち鉱酸水溶液で洗浄す
ることができ、あるいは逆に鉱酸水溶液で洗浄したのち
シュウ酸水溶液で洗浄することができる。シュウ酸水溶
液のみを用いる場合、シュウ酸濃度が１重量％未満であ
ると洗浄効果が小さく、シュウ酸濃度が１０重量％を超
えると洗浄効果は濃度の上昇に見合っては向上しない。
シュウ酸水溶液と鉱酸水溶液を併用する場合あるいはシ
ュウ酸と鉱酸の混合水溶液を用いる場合、シュウ酸濃度
が０.０５重量％未満であると洗浄効果が小さく、シュ
ウ酸濃度が１重量％を超えると洗浄効果は濃度の上昇に
見合っては向上しない。シュウ酸水溶液と併用する鉱酸
水溶液の濃度及びシュウ酸と鉱酸の混合水溶液中の鉱酸
の濃度は、３重量％未満であると洗浄効果が小さく、１
５重量％を超えると洗浄効果は濃度の上昇に見合っては
向上しない。膜に付着するＳＳ成分には、通常、シュウ
酸水溶液に可溶な成分と、鉱酸水溶液に可溶な成分とが
混在しているため、洗浄薬剤としてシュウ酸と鉱酸とを
混合し、両者を同時に作用させることにより高い洗浄効
果を得ることができるので好ましい。In the method of the present invention, when the membrane is contaminated by the use of the membrane and the amount of permeated water is reduced, the membrane is washed.
The membrane is washed by backwashing and chemical washing. Normally, the backwashing is suitably performed about once every 5 minutes to 5 hours. For example, pressurized air is sent from the compressor 8 to the treatment water tank 7, and the treated water is pressurized to increase the pressure from the permeation side of the membrane to the raw water side. And backwashing can be performed. Backwashing cannot completely remove dirt on the membrane surface,
Since the amount of permeated water gradually decreases, chemical cleaning is performed. In the method of the present invention, chemical cleaning is performed with a cleaning liquid containing oxalic acid. There is no particular limitation on the method of chemical cleaning using a cleaning solution containing oxalic acid. For example, the cleaning can be performed using an aqueous solution of oxalic acid having a concentration of 1 to 10% by weight, and a concentration of 0.05 to 1%.
The oxalic acid aqueous solution having a concentration of 3 to 15% by weight can be washed together with an aqueous solution of oxalic acid having a concentration of 3 to 15% by weight or a mixed aqueous solution containing 0.05 to 1% by weight of oxalic acid and 3 to 15% by weight of a mineral acid. Can be used for washing. When an oxalic acid aqueous solution and a mineral acid aqueous solution are used in combination, the order of washing is not limited, and it is possible to wash with an oxalic acid aqueous solution and then with a mineral acid aqueous solution, or conversely, wash with a mineral acid aqueous solution and then with oxalic acid. It can be washed with an aqueous solution. When only the oxalic acid aqueous solution is used, if the oxalic acid concentration is less than 1% by weight, the cleaning effect is small, and if the oxalic acid concentration exceeds 10% by weight, the cleaning effect is not improved in proportion to the increase in the concentration.
When the oxalic acid aqueous solution and the mineral acid aqueous solution are used in combination or the mixed aqueous solution of oxalic acid and the mineral acid is used, if the oxalic acid concentration is less than 0.05% by weight, the cleaning effect is small, and the oxalic acid concentration is 1% by weight. Above this, the cleaning effect does not improve in proportion to the increase in concentration. When the concentration of the aqueous mineral acid solution used in combination with the aqueous oxalic acid solution and the concentration of the mineral acid in the mixed aqueous solution of oxalic acid and the mineral acid are less than 3% by weight, the cleaning effect is small, and
If it exceeds 5% by weight, the cleaning effect does not improve in proportion to the increase in concentration. Since the SS component adhering to the film usually contains a component soluble in an oxalic acid aqueous solution and a component soluble in a mineral acid aqueous solution, oxalic acid and a mineral acid are mixed as a cleaning agent, It is preferable that both act at the same time, since a high cleaning effect can be obtained.
【０００８】本発明方法において、膜の薬品洗浄は膜の
原水側へシュウ酸水溶液又はシュウ酸と鉱酸の混合水溶
液を充填して行うことができる。膜とシュウ酸水溶液又
はシュウ酸と鉱酸の混合水溶液の接触の際の温度は、常
温〜８０℃とすることが好ましい。接触の際の温度を冷
却により常温未満としても特に利点はなく、むしろ洗浄
効果が小さくなるおそれがある。一般に膜とシュウ酸水
溶液又はシュウ酸と鉱酸の混合水溶液の接触の際の温度
を上昇すると洗浄効果は向上するが、８０℃を超える温
度とする必要は少なく、むしろ膜の劣化をはやめるおそ
れがある。膜とシュウ酸水溶液又はシュウ酸と鉱酸の混
合水溶液の接触時間は、１〜数１０時間であることが好
ましい。接触時間が１時間未満であると、膜の洗浄が十
分に行われないおそれがある。接触時間は数１０時間あ
れば十分であり、接触時間が数１０時間を超えても通常
は洗浄効果は向上しない。本発明方法においては、酸洗
浄に加えてアルカリ洗浄を行うことができる。アルカリ
洗浄はシリカ系スケールの除去に有効であり、膜の汚染
物質としてシリカが多い場合に好適に実施することがで
きる。使用するアルカリ洗浄液には特に制限はなく、例
えば、水酸化ナトリウム水溶液、水酸化カリウム水溶液
等を使用することができる。アルカリ洗浄液の濃度は、
４〜１５重量％とすることが好ましい。アルカリ洗浄液
は、常温又は加温した状態で、数時間、膜に充填又は循
環しながら膜に接触させることが好ましい。本発明方法
において、洗浄の順序は、酸洗浄後にアルカリ洗浄でも
よく、アルカリ洗浄後に酸洗浄でもよく、特に順序に制
限はない。図１に示した例では、アルカリ洗浄液はアル
カリ貯槽９に、鉱酸とシュウ酸との混合酸洗浄液は酸貯
槽１０に用意される。洗浄に際しては、まずポンプ１１
を駆動してアルカリ貯槽９のアルカリ洗浄液を膜分離装
置６の透過水側に供給し、配管を通ってアルカリ貯槽９
に戻り、所定時間アルカリ洗浄液が循環される。次にア
ルカリ洗浄液を濃縮水側に入れ、循環される。その後、
洗浄液は酸洗浄液に切り換えられ、酸貯槽１０の酸洗浄
液が同様にして酸貯槽１０と膜分離装置６との間を循環
され、膜を洗浄する。このようにして洗浄すると、排煙
脱硫排水特有の膜汚染物質が除去され、膜性能が回復す
る。そして、本発明方法の膜洗浄で発生した洗浄廃液
は、排煙脱硫排水の処理工程を利用することにより、別
途廃液処理装置を設けることなく処理することができ
る。図１の例において、膜モジュールの洗浄により発生
した洗浄廃液は、アルカリ性洗浄廃液をアルカリ貯槽９
及び酸性洗浄廃液を酸貯槽１０に分けて貯留する。アル
カリ性洗浄廃液は、洗浄に用いた水酸化ナトリウム、水
酸化カリウム等を含有する。酸性洗浄廃液は、シュウ酸
又はシュウ酸及び鉱酸を含有する。洗浄廃液は、ポンプ
１１により排煙脱硫排水に直接又は凝集反応槽に返送さ
れ、排煙脱硫排水と一定の割合で混合される。洗浄廃液
の返送量は、膜モジュールの洗浄頻度及び１回の洗浄に
使用する洗浄液の量によって決まるが、通常は排煙脱硫
排水の数十分の一の量であるので、排煙脱硫排水の処理
工程の運転効率を低下させることなく、洗浄廃液を返送
することができる。排煙脱硫排水は、通常、返送される
洗浄廃液中のシュウ酸を不溶性のシュウ酸カルシウムに
するに十分なカルシウムイオンを含有しているが、必要
に応じてpH調整に消石灰を用いる等の方法により被処理
水にカルシウムイオンを供給することができる。洗浄廃
液中のシュウ酸は、排煙脱硫排水の処理工程において中
和され、水不溶性のシュウ酸カルシウムとなり、凝集フ
ロックとともに膜分離装置で除去されるのでＣＯＤ負荷
とならず、シュウ酸除去のための薬剤や工程を必要とせ
ず、洗浄廃液は排煙脱硫排水と同時に処理される。ま
た、洗浄廃液を排煙脱硫排水に混合することにより、フ
ラックスはむしろ安定化する。この作用機構は明らかで
はないが、洗浄廃液を混合することによって生成するＳ
Ｓの粒子が膜処理に適したものとなるためと考えられ
る。本発明方法においては、排煙脱硫排水の処理工程と
して、必要に応じて、酸化工程、凝集工程及び膜分離以
外の任意の処理工程を、任意の段階に加えることができ
る。例えば、凝集工程で除去することができないイオン
性のＣＯＤ成分の除去のために、吸着樹脂、活性炭、イ
オン交換樹脂等を充填した吸着塔を設けることができ
る。また、要求処理水質によっては、フッ素の除去率を
向上させるために、フッ素吸着塔を設けることができ、
さらに重金属の除去効果をあげるために、凝集工程にお
いて重金属固定剤を併用することができる。In the method of the present invention, the chemical cleaning of the membrane can be carried out by filling the raw water side of the membrane with an oxalic acid aqueous solution or a mixed aqueous solution of oxalic acid and a mineral acid. The temperature at the time of contact between the membrane and the oxalic acid aqueous solution or the mixed aqueous solution of oxalic acid and mineral acid is preferably from room temperature to 80 ° C. There is no particular advantage even if the temperature at the time of contact is made lower than room temperature by cooling, and the cleaning effect may be reduced. In general, increasing the temperature at the time of contact between the film and an aqueous oxalic acid solution or a mixed aqueous solution of oxalic acid and a mineral acid improves the cleaning effect. However, it is not necessary to use a temperature higher than 80 ° C, and the deterioration of the film may be stopped. There is. The contact time between the membrane and the oxalic acid aqueous solution or the mixed aqueous solution of oxalic acid and mineral acid is preferably 1 to several tens of hours. If the contact time is less than 1 hour, the film may not be sufficiently washed. A contact time of several tens of hours is sufficient. Even if the contact time exceeds several tens of hours, the cleaning effect is not usually improved. In the method of the present invention, alkali cleaning can be performed in addition to acid cleaning. The alkali cleaning is effective for removing the silica-based scale, and can be suitably performed when the amount of silica as a contaminant in the film is large. There is no particular limitation on the alkaline cleaning solution used, and for example, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, or the like can be used. The concentration of the alkaline cleaning solution is
The content is preferably 4 to 15% by weight. It is preferable that the alkali cleaning liquid is brought into contact with the membrane while filling or circulating the membrane for several hours at room temperature or in a heated state. In the method of the present invention, the order of washing may be alkali washing after acid washing or acid washing after alkali washing, and the order is not particularly limited. In the example shown in FIG. 1, an alkaline cleaning liquid is prepared in an alkaline storage tank 9, and a mixed acid cleaning liquid of a mineral acid and oxalic acid is prepared in an acid storage tank 10. At the time of cleaning, first, pump 11
Is supplied to supply the alkaline cleaning liquid in the alkaline storage tank 9 to the permeated water side of the membrane separation device 6, and the alkaline storage tank 9 is passed through a pipe.
And the alkaline cleaning liquid is circulated for a predetermined time. Next, the alkaline cleaning liquid is put into the concentrated water side and circulated. afterwards,
The cleaning liquid is switched to the acid cleaning liquid, and the acid cleaning liquid in the acid storage tank 10 is similarly circulated between the acid storage tank 10 and the membrane separation device 6 to clean the membrane. This cleaning removes membrane contaminants peculiar to flue gas desulfurization effluent, and restores membrane performance. The cleaning waste liquid generated in the membrane cleaning according to the method of the present invention can be treated without using a separate waste liquid treatment apparatus by using a treatment process of flue gas desulfurization wastewater. In the example of FIG. 1, the washing waste liquid generated by washing the membrane module is an alkaline washing waste liquid in an alkaline storage tank 9.
And the acidic washing waste liquid is divided and stored in the acid storage tank 10. The alkaline washing waste liquid contains sodium hydroxide, potassium hydroxide and the like used for washing. The acidic washing waste liquid contains oxalic acid or oxalic acid and a mineral acid. The cleaning waste liquid is returned to the flue gas desulfurization wastewater directly or to the coagulation reaction tank by the pump 11, and is mixed with the flue gas desulfurization wastewater at a fixed ratio. The amount of cleaning waste liquid returned is determined by the frequency of cleaning the membrane module and the amount of cleaning liquid used for one cleaning operation. The washing waste liquid can be returned without lowering the operation efficiency of the processing step. Flue gas desulfurization effluent usually contains enough calcium ions to convert oxalic acid in the returned washing waste liquor into insoluble calcium oxalate.However, if necessary, a method such as using slaked lime for pH adjustment Thus, calcium ions can be supplied to the water to be treated. Oxalic acid in the washing waste liquid is neutralized in the treatment process of flue gas desulfurization effluent, becomes water-insoluble calcium oxalate, and is removed together with flocculated floc by a membrane separation device. The cleaning effluent is treated at the same time as the flue gas desulfurization effluent without requiring any chemicals or processes. Further, by mixing the washing waste liquid with the flue gas desulfurization wastewater, the flux is rather stabilized. The mechanism of this action is not clear, but the S generated by mixing the washing waste liquid is
It is considered that the particles of S become suitable for the film treatment. In the method of the present invention, as a treatment step of the flue gas desulfurization effluent, an optional treatment step other than the oxidation step, the coagulation step, and the membrane separation can be added to an arbitrary stage as needed. For example, an adsorption tower filled with an adsorption resin, activated carbon, an ion exchange resin, or the like can be provided to remove an ionic COD component that cannot be removed in the aggregation step. In addition, depending on the required treatment water quality, a fluorine adsorption tower can be provided to improve the fluorine removal rate,
In order to further enhance the effect of removing heavy metals, a heavy metal fixing agent can be used in the aggregation step.
【０００９】[0009]
【実施例】以下に、実施例を挙げて本発明をさらに詳細
に説明するが、本発明はこれらの実施例によりなんら限
定されるものではない。 実施例１ 火力発電所脱硫排水をポリプロピレン製チューブラ精密
ろ過膜（内径５.５mm、孔径０.２μｍ）で処理した。こ
の精密ろ過膜の純水フラックスは、２２.４ｍ3／ｍ2・da
y（at ０.５kg／cm2・２５℃）である。また、排水の水
質は、pH７.２、ＣＯＤMn２０mg／リットル、ＳＳ４１m
g／リットル、フッ素２０mg／リットル、マンガン３.６
mg／リットルであった。原水を酸化工程においてpH８.
５で空気酸化したのち、凝集反応槽でポリ塩化アルミニ
ウム及び過マンガン酸カリウムを添加して凝集反応を行
い、循環槽に送った。循環槽から循環ポンプを用いて膜
モジュールに送液し、膜透過水は処理水として放流し
た。膜分離条件は、膜面流速２ｍ／ｓ、水温３０〜４０
℃、循環水入口圧力約１kgf／cm2、循環水出口圧力約
０.６kgf／cm2、膜透過水量５ｍ3／ｍ2・day（定流量）
とした。処理水の水質は、pH６.９、ＣＯＤMn１８mg／
リットル、ＳＳ１mg／リットル以下、フッ素４.１mg／
リットル、マンガン０.１mg／リットル以下となった。
また、循環槽内の汚泥は、ＳＳ成分約２重量％まで濃縮
された。この条件で１ケ月運転した膜は、純水フラック
ス９.０ｍ3／ｍ2・dayとなった。この膜を、８重量％水
酸化ナトリウム水溶液を用いて６０℃で２時間洗浄し、
続いてシュウ酸０.１重量％を溶解した７重量％塩酸を
用いて２５℃で２時間洗浄した。膜の純水フラックスは
２１.６ｍ3／ｍ2・dayとなり、膜の回復率は９６.４％で
あった。 実施例２ 実施例１に用いたものと同じ条件の精密ろ過膜を用い
て、塩酸による洗浄と、シュウ酸水溶液による洗浄を逐
次行った。１ケ月運転後の純水フラックス９.０ｍ3／ｍ
2・dayとなった膜を、８重量％水酸化ナトリウム水溶液
を用いて６０℃で２時間洗浄し、続いて７重量％塩酸を
用いて２５℃で２時間洗浄し、さらに０.５重量％シュ
ウ酸水溶液を用いて２５℃で２時間洗浄した。膜の純水
フラックスは２２.１ｍ3／ｍ2・dayとなり、膜の回復率
は９８.７％であった。 実施例３ 実施例１に用いたものと同じ条件の精密ろ過膜を用い
て、シュウ酸水溶液による洗浄を行った。１ケ月運転後
の純水フラックス９.０ｍ3／ｍ2・dayとなった膜を、８
重量％水酸化ナトリウム水溶液を用いて６０℃で２時間
洗浄し、続いて５重量％シュウ酸水溶液を用いて２５℃
で２時間洗浄した。膜の純水フラックスは２１.１ｍ3／
ｍ2・dayとなり、膜の回復率は９４.２％であった。 比較例１ 実施例１に用いたものと同じ条件の精密ろ過膜を用い
て、シュウ酸を用いることなく、塩酸による洗浄のみを
行った。１ケ月運転後の純水フラックス９.０ｍ3／ｍ2・
dayとなった膜を、８重量％水酸化ナトリウム水溶液を
用いて６０℃で２時間洗浄し、続いて７.５重量％塩酸
を用いて２５℃で２時間洗浄した。膜の純水フラックス
は１９.６ｍ3／ｍ2・dayとなり、膜の回復率は８７.５％
であった。実施例１〜３のシュウ酸含む洗浄液を用いた
洗浄によると、精密ろ過膜の純水フラックスの回復率が
高く、膜の汚染が効率よく除去されているが、洗浄にシ
ュウ酸を用いない比較例１では、精密ろ過膜の純水フラ
ックスの回復率が低い。 実施例４ 火力発電所脱硫排水をポリプロピレン製チューブラ精密
ろ過膜（内径５.５mm、孔径０.２μｍ、膜面積０.０３
６ｍ2）で処理した。この精密ろ過膜のフラックスは、
１２.０ｍ3／ｍ2・ｄ（０.５kgf／cm2、２５℃換算）で
ある。また、排水の水質は、pH６.５、ＣＯＤMn２５mg
／リットル、ＳＳ１５０mg／リットル、フッ素２５mg／
リットル、マンガン３.０mg／リットル、カルシウム１,
５００mg／リットルであった。排水を酸化工程において
空気酸化したのち、反応槽でポリ塩化アルミニウム２,
０００mg／リットル及び過マンガン酸カリウム６.０mg
／リットルを添加し、水酸化ナトリウムによりpHを６.
５に調整して凝集反応を行い、循環槽に送った。循環槽
から循環ポンプを用いて膜モジュールに送液し、膜透過
水は処理水として放流した。膜分離条件は、膜面流速２
ｍ／ｓ、水温３０〜４０℃、循環水入口圧力１.０kgf／
cm2、循環水出口圧力０.８kgf／cm2、膜透過水量５ｍ3
／ｍ2・ｄ（定流量）とした。膜は、１５分間に１回、処
理水による１０秒間の逆流洗浄を行った。この条件で１
カ月運転したところ、処理水の水質はＣＯＤMn１９mg／
リットル、ＳＳ０mg／リットル、フッ素７.５mg／リッ
トル、マンガン０.２mg／リットルであった。なお、循
環槽内の汚泥は、ＳＳ成分約２重量％まで濃縮された。
また、フラックスは６.０ｍ3／ｍ2・ｄとなり、１日当た
りのフラックス低下率は、０.２０ｍ3／ｍ2・ｄ2（０.５
kgf／cm2、２５℃換算）であった。この膜を、８重量％
水酸化ナトリウム水溶液を用いて６０℃で５時間洗浄
し、純水で置換後、シュウ酸０.１重量％を溶解した７
重量％塩酸を用いて２５℃で２時間洗浄した。膜のフラ
ックスは、洗浄により１２.０ｍ3／ｍ2・ｄに回復した。
この洗浄の際に発生した洗浄廃液のＣＯＤMnは、８５mg
／リットルであった。この洗浄廃液を、排煙脱硫排水に
５容量％の割合で均一に添加しながら、反応槽における
凝集反応及び膜分離を継続した。最初の１カ月と同じ条
件で処理を行ったところ、処理水の水質はＣＯＤMn１９
mg／リットル、ＳＳ０mg／リットル、フッ素７.５mg／
リットル、マンガン０.２mg／リットルで、最初の１カ
月の処理水の水質と全く同じであった。また、４０日後
にフラックスが６.０ｍ3／ｍ2・ｄとなり、この間の１日
当たりのフラックス低下率は０.１５ｍ3／ｍ2・ｄ2であ
った。すなわち、１日当たりのフラックスの低下率は、
最初の１カ月よりも小さい。以上の結果から、シュウ酸
を含む膜洗浄廃液を排煙脱硫排水に添加し、処理した場
合も、処理水質には膜洗浄廃液を添加しない場合と変化
がなく、フラックスの低下率が抑制され、フラックスが
安定して洗浄頻度が少なくなることが分かった。EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 Desulfurization wastewater from a thermal power plant was treated with a tubular microfiltration membrane made of polypropylene (inner diameter 5.5 mm, pore diameter 0.2 μm). The pure water flux of this microfiltration membrane is 22.4m 3 / m 2 · da
y (at 0.5 kg / cm 2 · 25 ° C.). The water quality of the wastewater was pH 7.2, COD Mn 20 mg / liter, SS41m
g / liter, fluorine 20mg / liter, manganese 3.6
mg / liter. Raw water is oxidized to pH 8.
After air oxidation in step 5, polyaluminum chloride and potassium permanganate were added in an agglutination reaction tank to perform an agglutination reaction, which was sent to a circulation tank. The solution was sent from the circulation tank to the membrane module using a circulation pump, and the permeated water was discharged as treated water. The membrane separation conditions were as follows: membrane surface flow rate 2 m / s, water temperature 30-40.
° C, circulating water inlet pressure about 1 kgf / cm 2 , circulating water outlet pressure about 0.6 kgf / cm 2 , membrane permeated water volume 5 m 3 / m 2 · day (constant flow rate)
And The quality of the treated water is pH 6.9, COD Mn 18 mg /
Liter, SS 1 mg / liter or less, fluorine 4.1 mg /
Liters and manganese were less than 0.1 mg / liter.
The sludge in the circulation tank was concentrated to about 2% by weight of the SS component. The membrane operated under these conditions for one month had a pure water flux of 9.0 m 3 / m 2 · day. This membrane was washed with an 8% by weight aqueous solution of sodium hydroxide at 60 ° C. for 2 hours,
Subsequently, the resultant was washed at 25 ° C. for 2 hours using 7% by weight hydrochloric acid in which 0.1% by weight of oxalic acid was dissolved. The pure water flux of the membrane was 21.6 m 3 / m 2 · day, and the recovery rate of the membrane was 96.4%. Example 2 Using a microfiltration membrane under the same conditions as those used in Example 1, washing with hydrochloric acid and washing with an oxalic acid aqueous solution were sequentially performed. Pure water flux 9.0m 3 / m after one month operation
The 2 day film was washed with an 8% by weight aqueous sodium hydroxide solution at 60 ° C. for 2 hours, followed by a 7% by weight hydrochloric acid solution at 25 ° C. for 2 hours, and further with 0.5% by weight. The substrate was washed with an aqueous oxalic acid solution at 25 ° C. for 2 hours. The pure water flux of the membrane was 22.1 m 3 / m 2 · day, and the membrane recovery was 98.7%. Example 3 Washing with an oxalic acid aqueous solution was performed using a microfiltration membrane under the same conditions as those used in Example 1. The membrane that had a pure water flux of 9.0 m 3 / m 2 · day after one month operation was replaced with 8
2 hours at 60 ° C. using an aqueous solution of sodium hydroxide at a temperature of 25 ° C.
For 2 hours. The pure water flux of the membrane is 21.1 m 3 /
m 2 · day, and the recovery rate of the film was 94.2%. Comparative Example 1 Using a microfiltration membrane under the same conditions as those used in Example 1, only washing with hydrochloric acid was performed without using oxalic acid. Pure water flux 9.0m 3 / m 2・ after one month operation
The membrane at day was washed with an 8% by weight aqueous solution of sodium hydroxide at 60 ° C. for 2 hours, and subsequently with 7.5% by weight of hydrochloric acid at 25 ° C. for 2 hours. The pure water flux of the membrane was 19.6 m 3 / m 2 · day, and the recovery rate of the membrane was 87.5%
Met. According to the cleaning using the cleaning liquid containing oxalic acid in Examples 1 to 3, the recovery rate of the pure water flux of the microfiltration membrane is high, and the contamination of the membrane is efficiently removed, but the comparison does not use oxalic acid for cleaning. In Example 1, the recovery rate of the pure water flux of the microfiltration membrane is low. Example 4 The thermal power plant desulfurization effluent was treated with a polypropylene tubular microfiltration membrane (inner diameter 5.5 mm, pore diameter 0.2 μm, membrane area 0.03).
6 m 2 ). The flux of this microfiltration membrane is
It is 12.0 m 3 / m 2 · d (0.5 kgf / cm 2 , converted at 25 ° C.). The quality of the wastewater is pH 6.5, COD Mn 25mg
/ Liter, SS150mg / liter, fluorine 25mg /
Liter, manganese 3.0mg / liter, calcium 1,
It was 500 mg / liter. After the wastewater is oxidized with air in the oxidation process, the reaction tank is used
000 mg / liter and potassium permanganate 6.0 mg
Per liter and the pH is adjusted to 6.
The mixture was adjusted to 5 to carry out an agglutination reaction and sent to a circulation tank. The solution was sent from the circulation tank to the membrane module using a circulation pump, and the permeated water was discharged as treated water. The membrane separation conditions are as follows:
m / s, water temperature 30-40 ° C, circulating water inlet pressure 1.0kgf /
cm 2 , circulating water outlet pressure 0.8 kgf / cm 2 , membrane permeated water volume 5 m 3
/ M 2 · d (constant flow rate). The membrane was backwashed with treated water for 10 seconds once every 15 minutes. Under these conditions, 1
After months of operation, the quality of the treated water was COD Mn 19 mg /
Liter, SS 0 mg / l, fluorine 7.5 mg / l, manganese 0.2 mg / l. The sludge in the circulation tank was concentrated to about 2% by weight of the SS component.
The flux was 6.0 m 3 / m 2 · d, and the daily flux reduction rate was 0.20 m 3 / m 2 · d 2 (0.5
kgf / cm 2 at 25 ° C.). 8% by weight of this film
After washing with an aqueous sodium hydroxide solution at 60 ° C. for 5 hours, replacing with pure water, and dissolving 0.1% by weight of oxalic acid 7
Washing was performed at 25 ° C. for 2 hours using a weight% hydrochloric acid. The flux of the membrane was recovered to 12.0 m 3 / m 2 · d by washing.
The COD Mn of the washing waste liquid generated during this washing is 85 mg
/ Liter. The coagulation reaction and membrane separation in the reaction tank were continued while uniformly adding the washing waste liquid to the flue gas desulfurization wastewater at a ratio of 5% by volume. When treated under the same conditions as the first month, the quality of the treated water was COD Mn 19
mg / liter, SS0mg / liter, fluorine 7.5mg /
1 liter, 0.2 mg / liter of manganese was exactly the same as the quality of treated water for the first month. After 40 days, the flux was 6.0 m 3 / m 2 · d, and the rate of flux reduction per day during this period was 0.15 m 3 / m 2 · d 2 . That is, the rate of decrease in flux per day is
Less than the first month. From the above results, the membrane cleaning wastewater containing oxalic acid was added to the flue gas desulfurization wastewater, and even when treated, there was no change from the case where the membrane cleaning wastewater was not added to the treated water quality, and the rate of flux reduction was suppressed. It was found that the flux was stable and the frequency of cleaning was reduced.
【００１０】[0010]
【発明の効果】本発明方法によれば、二酸化マンガンの
ように鉱酸に難溶性のＳＳを含む排煙脱硫排水の膜処理
の膜洗浄において、高い性能回復率を保つことができ、
膜の長寿命化、ランニグクコスト低下の効果がある。さ
らに、膜洗浄廃液を排煙脱硫排水に混合することによ
り、膜洗浄廃液と排水を同時に処理し、洗浄廃液自体の
処理を省くことができ、装置全体の運転効率を高めるこ
とができる。さらに、洗浄廃液を排水に混合処理するこ
とにより、膜のフラックスが安定する。According to the method of the present invention, a high performance recovery rate can be maintained in membrane cleaning of flue gas desulfurization effluent containing SS which is hardly soluble in mineral acids such as manganese dioxide,
This has the effect of extending the life of the film and lowering the cost of the run. Further, by mixing the membrane cleaning waste liquid with the flue gas desulfurization waste water, the membrane cleaning waste liquid and the waste water can be simultaneously treated, and the treatment of the cleaning waste liquid itself can be omitted, and the operation efficiency of the entire apparatus can be improved. Furthermore, the flux of the membrane is stabilized by mixing the waste water with the waste water.
【図１】図１は、本発明の排煙脱硫排水の処理方法の一
態様の工程系統図である。FIG. 1 is a process flow chart of one embodiment of a method for treating flue gas desulfurization wastewater of the present invention.
１ 酸化工程 ２ 凝集反応槽 ３ pH計 ４ 循環槽 ５ 循環ポンプ ６ 膜分離装置 ７ 処理水槽 ８ コンプレッサー ９ アルカリ貯槽 １０ 酸貯槽 １１ ポンプ DESCRIPTION OF SYMBOLS 1 Oxidation process 2 Coagulation reaction tank 3 pH meter 4 Circulation tank 5 Circulation pump 6 Membrane separation device 7 Treatment water tank 8 Compressor 9 Alkaline storage tank 10 Acid storage tank 11 Pump
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 ＦＩ Ｃ０２Ｆ 9/00 ５０２ Ｃ０２Ｆ 9/00 ５０２Ｒ ５０３Ｇ ５０３ ５０４Ｂ ５０４ (72)発明者 松渓 直樹 東京都新宿区西新宿３丁目４番７号 栗田 工業株式会社内 (72)発明者 高土居 忠 東京都新宿区西新宿３丁目４番７号 栗田 工業株式会社内 (72)発明者 佐藤 武 東京都新宿区西新宿３丁目４番７号 栗田 工業株式会社内 (72)発明者 近沢 清仁 東京都新宿区西新宿３丁目４番７号 栗田 工業株式会社内──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. 6 Identification code FI C02F 9/00 502 C02F 9/00 502R 503G 503 504B 504 (72) Inventor Naoki Matsukei 3-4-2 Nishishinjuku, Shinjuku-ku, Tokyo No. Kurita Kogyo Co., Ltd. (72) Inventor Tadashi Takadoi 3- 4-7 Nishi Shinjuku, Shinjuku-ku, Tokyo Kurita Kogyo Co., Ltd. (72) Takeshi Sato 3-4-7 Nishi Shinjuku, Shinjuku-ku, Tokyo Kurita Kogyo Co., Ltd. (72) Inventor Kiyohito Chikazawa 3-4-7 Nishi Shinjuku, Shinjuku-ku, Tokyo Kurita Kogyo Co., Ltd.
Claims (2)
分離工程に通水して処理する排煙脱硫排水の処理方法に
おいて、処理の継続によって汚染した膜をシュウ酸を含
む洗浄液で洗浄することを特徴とする排煙脱硫排水の処
理方法。1. A method for treating flue gas desulfurization wastewater in which the flue gas desulfurization wastewater is passed through an oxidation step, a coagulation step, and a membrane separation step, wherein the membrane contaminated by the continuation of the treatment is treated with a cleaning liquid containing oxalic acid. A method for treating flue gas desulfurization wastewater, comprising washing.
することにより発生した洗浄廃液を、返送して排煙脱硫
排水に混合する請求項１記載の排煙脱硫排水の処理方
法。2. A method for treating flue gas desulfurization wastewater according to claim 1, wherein the washing wastewater generated by washing the contaminated film with a cleaning solution containing oxalic acid is returned and mixed with the flue gas desulfurization wastewater.
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|---|---|---|---|
| JP32219796A JP3871749B2 (en) | 1996-11-18 | 1996-11-18 | Treatment method of flue gas desulfurization waste water |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32219796A JP3871749B2 (en) | 1996-11-18 | 1996-11-18 | Treatment method of flue gas desulfurization waste water |
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| Publication Number | Publication Date |
|---|---|
| JPH10137542A true JPH10137542A (en) | 1998-05-26 |
| JP3871749B2 JP3871749B2 (en) | 2007-01-24 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
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