JP3905588B2 - Wastewater treatment method - Google Patents

Wastewater treatment method Download PDF

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Publication number
JP3905588B2
JP3905588B2 JP29119196A JP29119196A JP3905588B2 JP 3905588 B2 JP3905588 B2 JP 3905588B2 JP 29119196 A JP29119196 A JP 29119196A JP 29119196 A JP29119196 A JP 29119196A JP 3905588 B2 JP3905588 B2 JP 3905588B2
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Prior art keywords
fluorine
water
liter
treated
heavy metal
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JPH10113672A (en
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忠 高土居
武 佐藤
利夫 四元
誠一 今野
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Kurita Water Industries Ltd
Nihon Kaisui Co Ltd
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Kurita Water Industries Ltd
Nihon Kaisui Co Ltd
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Description

【0001】
【発明の属する技術分野】
本発明は、排水処理方法に関する。さらに詳しくは、本発明は、フッ素と重金属を含む排水を、イオウ化合物系重金属固定剤及び造粒酸化セリウムからなるフッ素吸着樹脂により処理し、重金属及びフッ素を低濃度まで除去するとともに、処理水中へのセリウムの溶出とフッ素吸着樹脂の劣化を防止することができる排水処理方法に関する。
【0002】
【従来の技術】
発電所排水や半導体製造排水の中には、フッ素と重金属が含まれる場合がある。従来、フッ素と重金属を含む排水の処理は、アルカリ性にして重金属類を不溶化し凝集処理する方法が一般的であったが、アルカリ性にすることにより除去する必要のない共存するマグネシウムイオンも水酸化マグネシウムとなって沈殿し、汚泥の発生量が増大していた。そのため、近年は、中性領域で凝集固液分離を行い、重金属を除去するために、イオウ化合物を同時に添加する方法が用いられている。
この凝集処理のみではフッ素の除去が不十分であるため、先の凝集処理でアルミニウム化合物を添加して共沈させる方法や、先の凝集処理水にアルミニウム化合物や水酸化ナトリウムを添加し、水酸化アルミニウムや水酸化マグネシウムを生成させて共沈処理する方法もあるが、沈殿池を2段に設けるため設備費が高く、また汚泥処分費も増大する欠点があった。
沈殿池を1段とする場合は、フッ素の高度処理のために設備面積の小さいフッ素吸着樹脂塔を設けることが有効であり、フッ素吸着樹脂としては造粒アルミナや造粒酸化セリウムなどが用いられる。しかし、造粒アルミナは再生をくり返すと樹脂強度が低下し、また、再生剤としてアルミニウム化合物を用いるために汚泥の生成量が多いなどの問題が残されている。一方、造粒酸化セリウムからなるフッ素吸着樹脂は、原水の通水工程において微量のセリウムが溶出する場合があり、フッ素吸着容量の減少や物理的強度の低下が生じ、長期間の安定した処理を行うには問題があった。
【0003】
【発明が解決しようとする課題】
本発明は、フッ素と重金属を含む排水を、イオウ化合物系重金属固定剤及び造粒酸化セリウムからなるフッ素吸着樹脂を用いて処理し、排水中のフッ素及び重金属の濃度を十分に低下させるとともに、処理水中へのセリウムの溶出とフッ素吸着樹脂の劣化を防止し、長期間の安定した処理を可能とする排水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。
【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、排水にイオウ化合物系重金属固定剤を添加して得られる固液分離水に、塩素剤を添加して酸化還元電位を600mV以上としたのち、フッ素吸着樹脂で処理することにより、処理水中へのセリウムの溶出を防止し得ることを見いだし、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)フッ素と重金属を含む排水を、イオウ化合物系重金属固定剤を添加し固液分離したのち、フッ素吸着樹脂と接触させて処理する方法であって、固液分離水のpHを2〜5にするとともに、塩素剤を添加して酸化還元電位を600mV以上とし、造粒酸化セリウムからなるフッ素吸着樹脂により処理することを特徴とする排水処理方法、
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、
(2)イオウ化合物系重金属固定剤が、高分子イオウ化合物である第(1)項記載の排水処理方法、
(3)固液分離水のpHを、3.0〜3.5に調整する第(1)項又は第(2)項記載の排水処理方法、
(4)塩素剤が、次亜塩素酸ナトリウムである第(1)項、第(2)項又は第(3)項記載の排水処理方法、
(5)酸化還元電位を、700〜950mVとする第(1)項、第(2)項、第(3)項又は第(4)項記載の排水処理方法、及び、
(6)固液分離水の酸化還元電位により、塩素剤の添加量を自動制御する第(1)項、第(2)項、第(3)項、第(4)項又は第(5)項記載の排水処理方法、
を挙げることができる。
【0005】
【発明の実施の形態】
本発明方法は、フッ素と重金属を含む排水に適用する。このようなフッ素と重金属を含む排水としては、火力発電所の排水や半導体製造工場の排水などを挙げることができる。図1は、本発明の排水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は、フッ素と重金属を含む排水を反応槽1へ導入し、pH調整剤を添加して、凝集処理に適するpH、例えば、pH6〜10に調整する。pH調整剤としては、通常はアルカリ剤を使用する。使用するアルカリ剤には特に制限はなく、例えば、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、炭酸カリウム、消石灰、カーバイド滓などを挙げることができるが、これらの中で水酸化ナトリウム及び消石灰を特に好適に使用することができる。
反応槽1において、さらに凝集剤を添加して、懸濁物質、フッ素及び重金属の大部分を除去する。使用する凝集剤には特に制限はなく、例えば、硫酸バンド、ポリ塩化アルミニウム、塩化アルミニウム、硫酸第一鉄、塩化第二鉄、消石灰などの無機凝集剤、アルギン酸ナトリウム、カルボキシメチルセルロース、ポリアクリルアミドの部分加水分解物の塩などのアニオン性高分子凝集剤、ポリエチレンイミン、ポリチオ尿素、ポリジメチルジアリルアンモニウムクロライドなどのカチオン性高分子凝集剤、ポリアクリルアミドなどのノニオン性高分子凝集剤などを挙げることができる。これらの凝集剤は、1種を単独で使用することができ、2種以上を組み合わせて使用することができる。また、凝集剤の一部は重金属固定剤添加の後に添加することができ、例えば、無機凝集剤を添加して凝集処理を行い、続いて重金属固定剤を添加して重金属の固定を行ったのち、さらに高分子凝集剤を添加して凝集物や不溶化物を粗大化し、分離性を向上することができる。
【0006】
pHを調整し、凝集剤を添加した排水には、さらにイオウ化合物系重金属固定剤を添加する。イオウ化合物系重金属固定剤の添加は、凝集剤の添加と同じ反応槽において行うことができ、あるいは、別に反応槽を設けてイオウ化合物系重金属固定剤を添加することができる。イオウ化合物系重金属固定剤の添加により、凝集剤によっては完全に除去しきれなかった残余の重金属を不溶化する。イオウ化合物系重金属固定剤としては、例えば、硫化ナトリウム、硫化水素ナトリウム、高分子イオウ化合物などを挙げることができる。高分子イオウ化合物としては、=C=S基を有するイオウ含有化合物、チオール基を有するイオウ含有化合物、ジチオカルバミン酸基を有するイオウ含有化合物などを挙げることができる。特に好適な高分子イオウ化合物としては、ジチオカルバミン酸基とチオール基をキレート形成基として有する化合物、例えば、栗田工業(株)製のウェルクリン(商品名)などは、その過剰分が鉄やアルミニウムの水酸化物と反応するので溶存量が少なくなり、臭気の発生も少ないので好適に使用することができる。重金属の硫化物の溶解度積は、一般に水酸化物の溶解度積より小さいので、イオウ化合物系重金属固定剤を使用することにより、重金属を低濃度まで除去することができる。
本発明方法においては、重金属固定処理後の被処理水について固液分離装置2において、固液分離を行う。固液分離装置には特に制限はなく、例えば、沈殿槽、浮上槽、ろ過器、遠心分離機、膜分離装置など任意の固液分離装置を使用することができる。これらの中で、膜分離装置は、微細な懸濁物質をも除去することができ、装置を小型化することが可能であるので、特に好適に使用することができる。また、沈殿槽や浮上槽を用いたときは、後段に砂ろ過などのろ過装置を設置することが好ましい。
【0007】
本発明方法においては、固液分離水を反応槽3に送り、pH調整剤を添加してpHを2〜5、好ましくは3.0〜3.5に調整するとともに、塩素剤を添加して酸化還元電位(ORP)を600mV以上、好ましくは700〜950mVとする。酸化還元電位はpH値によっても変動するので、pHを3.0〜3.5の範囲に制御することがより好ましい。固液分離水のpHが2未満であると、フッ素吸着樹脂が劣化するおそれがある。固液分離水のpHが5を超えると、水中に残留するイオウ化合物系重金属固定剤と塩素の反応が遅く、イオウ化合物系重金属固定剤がフッ素吸着樹脂塔に流入し、フッ素吸着樹脂を劣化させるおそれがある。固液分離水のpHが2〜5であると、水中に残留するイオウ化合物系重金属固定剤と塩素の反応が速やかに進行し、残留するイオウ化合物系重金属固定剤が効果的に除去される。反応槽3における滞留時間は、通常5〜30分程度とすることが好ましい。また、被処理水のpHが2〜5であると、フッ素吸着樹脂へのフッ素の吸着速度が速く、この点からも好都合である。pHを2〜5とするためのpH調整剤としては、例えば、塩酸、硫酸、硝酸などを使用することができるが、これらの中で塩酸を特に好適に使用することができる。使用する塩素剤は、遊離塩素を発生する薬剤であれば特に制限はなく、例えば、塩素ガス、次亜塩素酸ナトリウム、次亜塩素酸カルシウム、さらし粉、塩素化イソシアヌル酸などを挙げることができるが、これらの中で次亜塩素酸ナトリウムを特に好適に使用することができる。
本発明方法においては、塩素剤の添加量は、被処理水中に残留するイオウ化合物系重金属固定剤を除去するために必要十分な量とすることが好ましいが、適切な塩素剤の添加量は、被処理水の酸化還元電位を測定することにより、容易に制御することができる。すなわち、反応槽3中の被処理水に酸化還元電位計4の電極を浸漬し、酸化還元電位制御計5を介して、塩素剤貯槽6に連結したポンプ7を運転することにより、反応槽3の中の被処理水の酸化還元電位を自動的に、かつ正確に設定値に保つことができる。
【0008】
本発明方法において、被処理水の酸化還元電位が600mV未満であると、被処理水に重金属固定剤が残存し、造粒酸化セリウムからなるフッ素吸着樹脂からセリウムが溶出するおそれがある。セリウムの溶出は、酸化セリウムがイオウ化合物系重金属固定剤によって還元されるために生ずると考えられる。被処理水の酸化還元電位が1,000mVを超えても、セリウムが溶出することはないが、被処理水中の残留塩素濃度が高く、フッ素吸着樹脂を劣化させるおそれがあるので、被処理水の酸化還元電位は700〜950mVとすることが好ましい。被処理水の酸化還元電位が700〜950mVであると、被処理水中の残留塩素濃度は1〜17mg/リットル程度となる。
本発明方法において、反応槽3においてpHを2〜5、酸化還元電位を600mV以上に調整された被処理水は、ポンプ8によりフッ素吸着樹脂塔9へ送水される。フッ素吸着樹脂塔における通水は、下向流又は上向流のいずれでもよく、流速はSV3〜30hr-1とすることが好ましく、10〜20hr-1とすることがより好ましい。被処理水中に残存するフッ素は、フッ素吸着樹脂により吸着除去され、フッ素吸着樹脂塔から重金属、フッ素ともに低濃度まで除去され、かつセリウムの溶出のない処理水が流出する。処理水はpHを調整したのち、放流することができ、あるいは必要に応じて、高度処理や水回収工程に流入させることができる。本発明方法によれば、造粒酸化セリウムからなるフッ素吸着樹脂の性能の劣化を生じにくいので、フッ素吸着樹脂の再生、補充、交換の頻度が減少し、長期間にわたり安定してフッ素と重金属を含む排水を処理することができる。
【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
pHが5.7であり、懸濁物質52mg/リットル、水銀0.011mg/リットル、マンガン10mg/リットル、鉄40mg/リットル及びフッ素47mg/リットルを含有するスーツ混合型排煙脱硫排水に、水酸化ナトリウムを加えてpH7.5とし、3時間曝気した。さらに、ポリ塩化アルミニウム1,000mg/リットルを加え、水酸化ナトリウムを加えてpH6.5に調整し、高分子イオウ化合物[栗田工業(株)製、ウェルクリン]30mg/リットルとアニオン性高分子凝集剤0.5mg/リットルを添加して撹拌したのち、静置して上澄水を得た。上澄水の水質は、懸濁物質5mg/リットル以下、水銀0.0005mg/リットル以下、マンガン0.1mg/リットル以下、鉄0.05mg/リットル以下及びフッ素20mg/リットルであった。
この上澄水に塩酸を加えてpH3.0とし、次亜塩素酸ナトリウムを塩素添加量として0、30、40、65、70、75、85及び100mg/リットルとなるよう添加した塩素処理水を調製した。塩素処理水の酸化還元電位は、塩素添加量0mg/リットルのとき450mV、塩素添加量40mg/リットルのとき600mV、塩素添加量100mg/リットルのとき1,000mVであった。
これらの塩素処理水を、フッ素吸着樹脂[旭エンジニアリング(株)製、リードF]30mlに、SV10hr-1の流速で通水した。フッ素吸着樹脂は、水酸化ナトリウムで再生し、塩酸による処理を行ったのち、十分水洗したものを使用した。通水10時間後の処理水について、残留塩素、フッ素及びセリウムの分析を行った。塩素添加量0mg/リットルのとき、残留塩素0mg/リットル、フッ素0.3mg/リットル及びセリウム1.5mg/リットルであり、塩素添加量40mg/リットルのとき、残留塩素0.05mg/リットル、フッ素0.3mg/リットル及びセリウム0.2mg/リットルであり、塩素添加量100mg/リットルのとき、残留塩素25mg/リットル、フッ素0.3mg/リットル及びセリウム0.1mg/リットル以下であった。
すべての塩素処理水についての測定値を、第1表に示す。
【0010】
【表1】

Figure 0003905588
【0011】
第1表の結果から、塩素添加量が40mg/リットルで酸化還元電位が600mVである塩素処理水を用いたとき、フッ素吸着樹脂に通水した処理水中のセリウムの濃度は0.2mg/リットルとなり、塩素処理水の酸化還元電位がこれより高いときは、フッ素吸着樹脂に通水した処理水中のセリウムの濃度は常に0.2mg/リットル以下となる。また、塩素処理水の酸化還元電位が600mV未満のときは、フッ素吸着樹脂に通水した処理水中のセリウムの濃度は0.2mg/リットルを超え、酸化還元電位が低くなるとともに溶出するセリウムの濃度は高くなることが分かる。
【0012】
【発明の効果】
本発明方法によれば、フッ素と重金属を含む排水の、イオウ化合物系重金属固定剤及び酸化セリウムからなるフッ素吸着樹脂を用いる処理において、排水中のフッ素及び重金属の濃度を十分に低下させるとともに、処理水中へのセリウムの溶出を防止し、フッ素吸着樹脂の劣化が生じにくく、長期間にわたる安定した処理が可能となる。
【図面の簡単な説明】
【図1】図1は、本発明の排水処理方法の一態様の工程系統図である。
【符号の説明】
1 反応槽
2 固液分離装置
3 反応槽
4 酸化還元電位計
5 酸化還元電位制御計
6 塩素剤貯槽
7 ポンプ
8 ポンプ
9 フッ素吸着樹脂塔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment method. More specifically, the present invention treats wastewater containing fluorine and heavy metals with a fluorine adsorption resin composed of a sulfur compound heavy metal fixing agent and granulated cerium oxide to remove heavy metals and fluorine to a low concentration, and into the treated water. The present invention relates to a wastewater treatment method capable of preventing elution of cerium and deterioration of a fluorine adsorption resin.
[0002]
[Prior art]
There are cases where fluorine and heavy metals are contained in power plant wastewater and semiconductor manufacturing wastewater. Conventionally, wastewater containing fluorine and heavy metals has been generally treated by making it alkaline and insolubilizing and aggregating heavy metals, but coexisting magnesium ions that do not need to be removed by making them alkaline are also magnesium hydroxide. As a result, the amount of sludge generated increased. Therefore, in recent years, a method of simultaneously adding a sulfur compound has been used in order to perform agglomeration solid-liquid separation in a neutral region and remove heavy metals.
Since the removal of fluorine is insufficient only by this agglomeration treatment, a method of coprecipitation by adding an aluminum compound in the previous agglomeration treatment, or by adding an aluminum compound or sodium hydroxide to the agglomeration treatment water, There is a method of coprecipitation treatment by producing aluminum or magnesium hydroxide, but there are drawbacks in that the installation cost is high because the sedimentation basin is provided in two stages and the sludge disposal cost is increased.
In the case of a single sedimentation basin, it is effective to provide a fluorine adsorption resin tower with a small equipment area for advanced fluorine treatment, and granulated alumina, granulated cerium oxide, etc. are used as the fluorine adsorption resin. . However, when granulated alumina is repeatedly regenerated, the strength of the resin decreases, and the use of an aluminum compound as a regenerant still causes problems such as a large amount of sludge generated. On the other hand, a fluorine-adsorbing resin made of granulated cerium oxide may cause a trace amount of cerium to elute during the raw water flow process, resulting in a decrease in fluorine adsorption capacity and a decrease in physical strength. There was a problem to do.
[0003]
[Problems to be solved by the invention]
The present invention treats wastewater containing fluorine and heavy metals with a fluorine adsorption resin comprising a sulfur compound-based heavy metal fixing agent and granulated cerium oxide, and sufficiently reduces the concentration of fluorine and heavy metals in the wastewater. The object of the present invention is to provide a wastewater treatment method that prevents elution of cerium into water and deterioration of the fluorine-adsorbing resin and enables stable treatment for a long period of time.
[0004]
[Means for Solving the Problems]
As a result of intensive research to solve the above problems, the present inventors have added a chlorinating agent to solid-liquid separated water obtained by adding a sulfur compound heavy metal fixing agent to the wastewater, thereby increasing the oxidation-reduction potential. After setting to 600 mV or more, it was found that elution of cerium into the treated water can be prevented by treating with a fluorine-adsorbing resin, and the present invention has been completed based on this finding.
That is, the present invention
(1) Waste water containing fluorine and heavy metal is treated by bringing a sulfur compound heavy metal fixing agent into solid-liquid separation and then contacting it with a fluorine-adsorbing resin. And a wastewater treatment method characterized by adding a chlorine agent to an oxidation-reduction potential of 600 mV or more and treating with a fluorine-adsorbing resin comprising granulated cerium oxide,
Is to provide.
Furthermore, as a preferred embodiment of the present invention,
(2) The wastewater treatment method according to item (1), wherein the sulfur compound-based heavy metal fixing agent is a polymer sulfur compound;
(3) The wastewater treatment method according to (1) or (2), wherein the pH of the solid-liquid separated water is adjusted to 3.0 to 3.5,
(4) The wastewater treatment method according to (1), (2) or (3), wherein the chlorinating agent is sodium hypochlorite,
(5) The wastewater treatment method according to (1), (2), (3), or (4), wherein the redox potential is 700 to 950 mV, and
(6) Item (1), Item (2), Item (3), Item (4) or Item (5) for automatically controlling the amount of chlorinating agent added by the redox potential of solid-liquid separated water Wastewater treatment method described in the section,
Can be mentioned.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The method of the present invention is applied to waste water containing fluorine and heavy metals. Examples of such wastewater containing fluorine and heavy metals include wastewater from thermal power plants and wastewater from semiconductor manufacturing plants. FIG. 1 is a process flow diagram of one embodiment of the wastewater treatment method of the present invention. In the method of the present invention, waste water containing fluorine and heavy metal is introduced into the reaction tank 1 and a pH adjuster is added to adjust the pH to a suitable pH for the coagulation treatment, for example, pH 6-10. As the pH adjuster, an alkali agent is usually used. There is no restriction | limiting in particular in the alkali agent to be used, For example, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, slaked lime, carbide slag etc. can be mentioned, Among these, sodium hydroxide and slaked lime are especially It can be preferably used.
In the reaction vessel 1, a flocculant is further added to remove most of the suspended substances, fluorine and heavy metals. There is no particular limitation on the flocculant used, for example, sulfuric acid band, polyaluminum chloride, aluminum chloride, ferrous sulfate, ferric chloride, inorganic flocculants such as slaked lime, sodium alginate, carboxymethylcellulose, polyacrylamide Anionic polymer flocculants such as hydrolyzate salts, cationic polymer flocculants such as polyethyleneimine, polythiourea and polydimethyldiallylammonium chloride, and nonionic polymer flocculants such as polyacrylamide . These flocculants can be used individually by 1 type, and can be used in combination of 2 or more type. In addition, a part of the flocculant can be added after the heavy metal fixing agent is added. For example, after adding the inorganic flocculant to perform the aggregating treatment and subsequently adding the heavy metal fixing agent, the heavy metal is fixed. Further, a polymer flocculant can be added to coarsen the agglomerates and insolubilized substances and improve the separability.
[0006]
A sulfur compound heavy metal fixing agent is further added to the wastewater to which the pH is adjusted and the flocculant is added. The addition of the sulfur compound heavy metal fixing agent can be performed in the same reaction vessel as the addition of the flocculant, or the sulfur compound heavy metal fixing agent can be added in a separate reaction vessel. The addition of the sulfur compound heavy metal fixing agent insolubilizes the remaining heavy metal that could not be completely removed by the flocculant. Examples of the sulfur compound-based heavy metal fixing agent include sodium sulfide, sodium hydrogen sulfide, and a polymer sulfur compound. Examples of the polymeric sulfur compound include a sulfur-containing compound having a ═C═S group, a sulfur-containing compound having a thiol group, and a sulfur-containing compound having a dithiocarbamic acid group. Particularly suitable high molecular weight sulfur compounds include compounds having dithiocarbamic acid groups and thiol groups as chelate-forming groups, such as Wellclin (trade name) manufactured by Kurita Kogyo Co., Ltd., whose excess is iron or aluminum. Since it reacts with the hydroxide, the dissolved amount is reduced and the generation of odor is small, so that it can be suitably used. Since the solubility product of sulfides of heavy metals is generally smaller than the solubility product of hydroxides, heavy metals can be removed to a low concentration by using a sulfur compound-based heavy metal fixing agent.
In the method of the present invention, solid-liquid separation is performed in the solid-liquid separation device 2 for the water to be treated after the heavy metal fixing treatment. There is no restriction | limiting in particular in a solid-liquid separator, For example, arbitrary solid-liquid separators, such as a sedimentation tank, a floating tank, a filter, a centrifuge, and a membrane separator, can be used. Among these, the membrane separation device can remove fine suspended solids and can be downsized, so that it can be used particularly preferably. Moreover, when a sedimentation tank or a levitation tank is used, it is preferable to install a filtration device such as sand filtration in the subsequent stage.
[0007]
In the method of the present invention, the solid-liquid separated water is sent to the reaction tank 3 and a pH adjuster is added to adjust the pH to 2 to 5, preferably 3.0 to 3.5, and a chlorine agent is added. The oxidation-reduction potential (ORP) is 600 mV or more, preferably 700 to 950 mV. Since the oxidation-reduction potential varies depending on the pH value, it is more preferable to control the pH within the range of 3.0 to 3.5. If the pH of the solid-liquid separation water is less than 2, the fluorine adsorption resin may be deteriorated. When the pH of the solid-liquid separation water exceeds 5, the reaction between the sulfur compound heavy metal fixing agent remaining in the water and chlorine is slow, and the sulfur compound heavy metal fixing agent flows into the fluorine adsorption resin tower and degrades the fluorine adsorption resin. There is a fear. When the pH of the solid-liquid separation water is 2 to 5, the reaction between the sulfur compound heavy metal fixing agent remaining in water and chlorine proceeds rapidly, and the remaining sulfur compound heavy metal fixing agent is effectively removed. The residence time in the reaction tank 3 is usually preferably about 5 to 30 minutes. Further, when the pH of the water to be treated is 2 to 5, the adsorption rate of fluorine to the fluorine adsorption resin is fast, which is advantageous from this point. As the pH adjuster for adjusting the pH to 2 to 5, for example, hydrochloric acid, sulfuric acid, nitric acid and the like can be used, and among these, hydrochloric acid can be particularly preferably used. The chlorine agent to be used is not particularly limited as long as it is a chemical that generates free chlorine, and examples thereof include chlorine gas, sodium hypochlorite, calcium hypochlorite, bleached powder, chlorinated isocyanuric acid, and the like. Of these, sodium hypochlorite can be particularly preferably used.
In the method of the present invention, the addition amount of the chlorine agent is preferably an amount necessary and sufficient to remove the sulfur compound-based heavy metal fixing agent remaining in the water to be treated. It can be easily controlled by measuring the redox potential of the water to be treated. That is, the electrode of the oxidation-reduction potentiometer 4 is immersed in the water to be treated in the reaction tank 3, and the pump 7 connected to the chlorine agent storage tank 6 is operated via the oxidation-reduction potential controller 5. It is possible to automatically and accurately maintain the redox potential of the water to be treated in the set value.
[0008]
In the method of the present invention, if the oxidation-reduction potential of the water to be treated is less than 600 mV, the heavy metal fixing agent remains in the water to be treated, and cerium may be eluted from the fluorine-adsorbing resin made of granulated cerium oxide. Elution of cerium is considered to occur because cerium oxide is reduced by a sulfur compound-based heavy metal fixing agent. Even if the oxidation-reduction potential of the water to be treated exceeds 1,000 mV, cerium does not elute, but the residual chlorine concentration in the water to be treated is high and there is a possibility of deteriorating the fluorine adsorption resin. The redox potential is preferably 700 to 950 mV. When the oxidation-reduction potential of the water to be treated is 700 to 950 mV, the residual chlorine concentration in the water to be treated is about 1 to 17 mg / liter.
In the method of the present invention, the water to be treated whose pH is adjusted to 2 to 5 and the oxidation-reduction potential is adjusted to 600 mV or higher in the reaction tank 3 is sent to the fluorine adsorption resin tower 9 by the pump 8. Passing water in fluorocarbon adsorption resin column may be either a downflow or upflow, it is preferable that the flow rate and SV3~30hr -1, and more preferably a 10~20hr -1. Fluorine remaining in the water to be treated is adsorbed and removed by the fluorine adsorbing resin, and both heavy metals and fluorine are removed from the fluorine adsorbing resin tower to a low concentration, and treated water without cerium elution flows out. The treated water can be discharged after adjusting the pH, or can be flowed into an advanced treatment or water recovery process as necessary. According to the method of the present invention, the performance of the fluorine-adsorbing resin made of granulated cerium oxide is hardly deteriorated, so the frequency of regeneration, replenishment and replacement of the fluorine-adsorbing resin is reduced, and fluorine and heavy metals are stably added over a long period of time. Wastewater containing can be treated.
[0009]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
Hydroxide is applied to a suit-mixed flue gas desulfurization effluent containing pH 5.7, suspended matter 52 mg / liter, mercury 0.011 mg / liter, manganese 10 mg / liter, iron 40 mg / liter and fluorine 47 mg / liter. Sodium was added to adjust the pH to 7.5 and aeration was performed for 3 hours. Furthermore, 1,000 mg / liter of polyaluminum chloride is added, and sodium hydroxide is added to adjust the pH to 6.5. Polymer sulfur compound [Welclin, manufactured by Kurita Kogyo Co., Ltd.] and anionic polymer aggregation 0.5 mg / liter of the agent was added and stirred, and then allowed to stand to obtain supernatant water. The quality of the supernatant water was 5 mg / liter or less of suspended solids, 0.0005 mg / liter or less of mercury, 0.1 mg / liter or less of manganese, 0.05 mg / liter or less of iron and 20 mg / liter of fluorine.
Prepare chlorinated water by adding hydrochloric acid to the supernatant water to pH 3.0, and adding sodium hypochlorite to 0, 30, 40, 65, 70, 75, 85, and 100 mg / liter as chlorine addition amount. did. The oxidation-reduction potential of chlorinated water was 450 mV when the chlorine addition amount was 0 mg / liter, 600 mV when the chlorine addition amount was 40 mg / liter, and 1,000 mV when the chlorine addition amount was 100 mg / liter.
These chlorinated waters were passed through 30 ml of fluorine adsorbing resin [Asahi Engineering Co., Ltd., Lead F] at a flow rate of SV10 hr- 1 . The fluorine-adsorbing resin was regenerated with sodium hydroxide, treated with hydrochloric acid, and washed thoroughly with water. Residual chlorine, fluorine and cerium were analyzed for the treated water after 10 hours of water flow. When the chlorine addition amount is 0 mg / liter, the residual chlorine is 0 mg / liter, fluorine is 0.3 mg / liter, and cerium is 1.5 mg / liter. When the chlorine addition amount is 40 mg / liter, the residual chlorine is 0.05 mg / liter, and the fluorine is zero. The residual chlorine was 25 mg / liter, the fluorine was 0.3 mg / liter, and the cerium was 0.1 mg / liter or less when the chlorine addition amount was 100 mg / liter.
Table 1 shows the measured values for all chlorinated water.
[0010]
[Table 1]
Figure 0003905588
[0011]
From the results in Table 1, when chlorinated water with a chlorine addition amount of 40 mg / liter and an oxidation-reduction potential of 600 mV was used, the concentration of cerium in the treated water passed through the fluorine-adsorbed resin was 0.2 mg / liter. When the oxidation-reduction potential of chlorinated water is higher than this, the concentration of cerium in the treated water that has passed through the fluorine-adsorbing resin is always 0.2 mg / liter or less. In addition, when the oxidation-reduction potential of chlorinated water is less than 600 mV, the concentration of cerium in the treated water that has passed through the fluorine adsorption resin exceeds 0.2 mg / liter, and the concentration of cerium that elutes as the oxidation-reduction potential decreases. Can be seen to be higher.
[0012]
【The invention's effect】
According to the method of the present invention, in the treatment of wastewater containing fluorine and heavy metal using a fluorine-adsorbing resin composed of a sulfur compound-based heavy metal fixing agent and cerium oxide, the concentration of fluorine and heavy metal in the wastewater is sufficiently reduced and treated. The elution of cerium into water is prevented, the fluorine adsorption resin is hardly deteriorated, and stable treatment over a long period of time is possible.
[Brief description of the drawings]
FIG. 1 is a process flow diagram of one embodiment of a wastewater treatment method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Solid-liquid separator 3 Reaction tank 4 Redox potential meter 5 Redox potential controller 6 Chlorine agent storage tank 7 Pump 8 Pump 9 Fluorine adsorption resin tower

Claims (1)

フッ素と重金属を含む排水を、イオウ化合物系重金属固定剤を添加し固液分離したのち、フッ素吸着樹脂と接触させて処理する方法であって、固液分離水のpHを2〜5にするとともに、塩素剤を添加して酸化還元電位を600mV以上とし、造粒酸化セリウムからなるフッ素吸着樹脂により処理することを特徴とする排水処理方法。Waste water containing fluorine and heavy metals is treated by adding a sulfur compound heavy metal fixing agent and solid-liquid separation, and then contacting with fluorine adsorption resin, and the pH of the solid-liquid separation water is adjusted to 2-5. A wastewater treatment method characterized by adding a chlorine agent to bring the oxidation-reduction potential to 600 mV or more and treating with a fluorine-adsorbing resin made of granulated cerium oxide.
JP29119196A 1996-10-14 1996-10-14 Wastewater treatment method Expired - Fee Related JP3905588B2 (en)

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