JP4507267B2 - Water treatment method - Google Patents
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- JP4507267B2 JP4507267B2 JP20232499A JP20232499A JP4507267B2 JP 4507267 B2 JP4507267 B2 JP 4507267B2 JP 20232499 A JP20232499 A JP 20232499A JP 20232499 A JP20232499 A JP 20232499A JP 4507267 B2 JP4507267 B2 JP 4507267B2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims description 101
- 238000000034 method Methods 0.000 title claims description 46
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 74
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims description 45
- 239000011669 selenium Substances 0.000 claims description 45
- 229910052711 selenium Inorganic materials 0.000 claims description 44
- 239000011737 fluorine Substances 0.000 claims description 42
- 229910052731 fluorine Inorganic materials 0.000 claims description 42
- 239000012528 membrane Substances 0.000 claims description 39
- 238000000926 separation method Methods 0.000 claims description 37
- 229910052742 iron Inorganic materials 0.000 claims description 26
- 239000007788 liquid Substances 0.000 claims description 18
- CWYNVVGOOAEACU-UHFFFAOYSA-N iron (II) ion Substances [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 17
- 239000007800 oxidant agent Substances 0.000 claims description 16
- 239000000126 substance Substances 0.000 claims description 15
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 14
- 229960004887 ferric hydroxide Drugs 0.000 claims description 14
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 claims description 14
- 230000002378 acidificating effect Effects 0.000 claims description 13
- 239000000701 coagulant Substances 0.000 claims description 5
- 238000010828 elution Methods 0.000 claims description 3
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 41
- 239000002351 wastewater Substances 0.000 description 21
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 20
- 238000006477 desulfuration reaction Methods 0.000 description 17
- 230000023556 desulfurization Effects 0.000 description 17
- 230000004907 flux Effects 0.000 description 17
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 16
- 239000003546 flue gas Substances 0.000 description 16
- 239000007787 solid Substances 0.000 description 14
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 13
- 238000005345 coagulation Methods 0.000 description 11
- 230000015271 coagulation Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 11
- 230000007423 decrease Effects 0.000 description 8
- 230000002776 aggregation Effects 0.000 description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 238000005273 aeration Methods 0.000 description 6
- 230000007935 neutral effect Effects 0.000 description 6
- 238000004220 aggregation Methods 0.000 description 5
- 239000003513 alkali Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 5
- 239000008394 flocculating agent Substances 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 239000006228 supernatant Substances 0.000 description 5
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 4
- 239000000347 magnesium hydroxide Substances 0.000 description 4
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000006722 reduction reaction Methods 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 3
- 239000000920 calcium hydroxide Substances 0.000 description 3
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 3
- 235000011116 calcium hydroxide Nutrition 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 238000005189 flocculation Methods 0.000 description 3
- 230000016615 flocculation Effects 0.000 description 3
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 3
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 3
- 229910021506 iron(II) hydroxide Inorganic materials 0.000 description 3
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 3
- 239000002923 metal particle Substances 0.000 description 3
- 238000001471 micro-filtration Methods 0.000 description 3
- -1 selenate ions Chemical class 0.000 description 3
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 229910001882 dioxygen Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000003002 pH adjusting agent Substances 0.000 description 2
- 229920002401 polyacrylamide Polymers 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 description 1
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 229910001341 Crude steel Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 229920002873 Polyethylenimine Polymers 0.000 description 1
- 229920006318 anionic polymer Polymers 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
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- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 244000144992 flock Species 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000002506 iron compounds Chemical class 0.000 description 1
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 238000005339 levitation Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 229910000027 potassium carbonate Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 150000003242 quaternary ammonium salts Chemical class 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- SPVXKVOXSXTJOY-UHFFFAOYSA-N selane Chemical compound [SeH2] SPVXKVOXSXTJOY-UHFFFAOYSA-N 0.000 description 1
- 229940006163 selenate ion Drugs 0.000 description 1
- 229940005981 selenite ion Drugs 0.000 description 1
- MCAHWIHFGHIESP-UHFFFAOYSA-L selenite(2-) Chemical compound [O-][Se]([O-])=O MCAHWIHFGHIESP-UHFFFAOYSA-L 0.000 description 1
- 239000000661 sodium alginate Substances 0.000 description 1
- 235000010413 sodium alginate Nutrition 0.000 description 1
- 229940005550 sodium alginate Drugs 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- PVGBHEUCHKGFQP-UHFFFAOYSA-N sodium;n-[5-amino-2-(4-aminophenyl)sulfonylphenyl]sulfonylacetamide Chemical compound [Na+].CC(=O)NS(=O)(=O)C1=CC(N)=CC=C1S(=O)(=O)C1=CC=C(N)C=C1 PVGBHEUCHKGFQP-UHFFFAOYSA-N 0.000 description 1
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Images
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- Separation Of Suspended Particles By Flocculating Agents (AREA)
- Removal Of Specific Substances (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、水処理方法に関する。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などのセレンとフッ素と懸濁物質を含有する排水を膜分離により処理して、膜フラックスの低下が少なく、かつセレンとフッ素を効率的に除去し得る水処理方法に関する。
【０００２】
【従来の技術】
石炭火力発電所などにおいて発生する排煙脱硫排水は、懸濁物質のほかに、セレン、フッ素などの有害物質を含有するので、水処理によってこれらの物質を除去する必要がある。排水中のセレンは、通常コロイド状のセレン、４価の亜セレン酸イオン（ＳｅＯ3 2-）又は６価のセレン酸イオン（ＳｅＯ4 2-）として存在することが多い。これらの中で、６価のセレン酸イオンの除去が特に困難であるために、さまざまな水処理方法が提案されている。
例えば、特開平９−１８７７７８号公報には、排煙脱硫装置から排出されるセレン、フッ素などの有害物質を含む排水を効率的に処理する方法として、排煙脱硫排水のpHを５以下に調整して鉄と接触させたのち、凝集処理及び固液分離を行う排煙脱硫排水の処理方法が提案されている。しかし、この方法では、フッ素の除去に要する凝集剤の量が多く、また、固液分離方法として膜分離を用いると、凝集処理において被処理水がアルカリ性とされているので、膜に水酸化マグネシウムなどのスケールが付着してフラックスが低下するという問題がある。また、特開平１１−２８４７５号公報には、処理水中のセレン濃度を排水基準である０.１mg／Ｌまで効率よく除去することができる処理方法として、セレン含有水を酸性条件下で鉄と接触させて処理する工程と、この処理水のpHを略中性に調整したのち過酸化物と接触させる工程と、高分子凝集剤で凝集後膜分離する工程とを有するセレン含有水の処理方法が提案されている。しかし、この方法によっては排水中のフッ素を十分に除去することができないので、排水がフッ素を含有する場合には、後段にフッ素吸着塔を設置する必要がある。さらに、多量の懸濁物質を含むセレン含有排水をそのまま鉄金属粒子層に通水して排水中のセレンを還元処理すると、鉄金属粒子の還元性能が低下することが明らかとなった。
このために、セレン、フッ素などの有害物質及び懸濁物質を含む排水から、これらの物質を効率的に除去することができ、しかも分離膜のフラックスの低下が少ない水処理方法が求められていた。
【０００３】
【発明が解決しようとする課題】
本発明は、石炭火力発電所の排煙脱硫排水などのセレンとフッ素と懸濁物質を含有する排水を膜分離により処理して、膜フラックスの低下が少なく、かつセレンとフッ素を効率的に除去し得る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、セレンとフッ素を含む水を凝集固液分離して、フッ素の大部分を除去したのち、酸性条件で鉄と接触させて鉄(II)イオンを溶出させ、酸化剤と反応させて水酸化第二鉄を析出させ、無機凝集剤を添加したのち膜分離することにより、膜フラックスの低下が少なく、セレンとフッ素を効率的に除去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）セレン及びフッ素を含有する水を、(Ａ)凝集剤を添加して凝集固液分離して、懸濁物質濃度を３００ｍｇ／Ｌ以下の分離後の水を得て、(Ｂ)該分離後の水を酸性条件で鉄と接触させて鉄(II)イオンを溶出させたのち、(Ｃ)酸化剤と反応させることにより水酸化第二鉄を析出させ、さらに(Ｄ)無機凝集剤を添加して、(Ｅ)膜分離することを特徴とする水処理方法、
（２）酸化剤が空気である第(１)項記載の水処理方法、及び、
（３）(Ｄ)無機凝集剤がポリ塩化アルミニウムである第(１)項又は第(２)項記載の水処理方法、
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、
（４）セレン及びフッ素を含有する水が、さらに懸濁物質を含む水である第(１)項記載の水処理方法、
（５）セレン、フッ素及び懸濁物質を含む水が、石炭火力発電所の排煙脱硫排水である第(４)項記載の水処理方法、
（６）(Ｂ)鉄との接触を、鉄金属充填層に通水することにより行う第(１)項記載の水処理方法、
（７）(Ｃ)酸化剤との反応をｐＨ６〜９で行う第(１)項記載の水処理方法、及び、
（８）(Ｄ)無機凝集剤を添加して、ｐＨ６〜８で凝集反応を行う第(１)項記載の水処理方法、
を挙げることができる。
【０００５】
【発明の実施の形態】
本発明の水処理方法は、セレン及びフッ素を含有する水を、(Ａ)凝集剤を添加して凝集固液分離し、(Ｂ)酸性条件で鉄と接触させて鉄(II)イオンを溶出させたのち、(Ｃ)酸化剤と反応させることにより水酸化第二鉄を析出させ、さらに(Ｄ)無機凝集剤を添加して、(Ｅ)膜分離するものである。本発明方法は、石炭火力発電所の排煙脱硫排水の処理に好適に適用することができる。
本発明方法においては、セレン及びフッ素を含む水に、(Ａ)凝集剤を添加して凝集固液分離する。使用する凝集剤に特に制限はなく、例えば、硫酸バンド、ポリ塩化アルミニウム、硫酸第一鉄、塩化第二鉄、消石灰、水酸化マグネシウムなどの無機凝集剤、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、第四級アンモニウム塩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。特に、フッ素の除去性能の高い無機凝集剤が好ましい。これらの凝集剤は、１種を単独で用いることができ、あるいは、２種以上を組み合わせて用いることもできる。セレン及びフッ素を含む水に凝集剤を添加することにより、懸濁物質の大部分が凝集してフロックを形成するとともに、水中のフッ素がフロックに吸着されて除去される。凝集したフロックの分離除去方法に特に制限はなく、例えば、沈殿、浮上、遠心分離、サイクロンなどを挙げることができる。
本発明方法においては、(Ｄ)無機凝集剤を添加する後工程を有するので、最初の(Ａ)凝集固液分離においては、フッ素と懸濁物質の一部が残存しても支障は生じない。したがって、凝集したフロックを高度に除去する必要はなく、簡易な設備を用いることができる。最初に懸濁物質を除去しておくことにより、(Ｂ)酸性条件に調整する際に、懸濁物質の溶解に消費される酸の量が減少し、経済的に水処理を行うことができる。凝集固液分離後の水中の懸濁物質濃度は、３００mg／Ｌ以下であることが好ましく、１００mg／Ｌ以下であることがより好ましい。凝集固液分離後の水中の懸濁物質濃度が３００mg／Ｌを超えると、(Ｂ)酸性条件での鉄との接触において、鉄の溶出が阻害されて鉄(II)イオンの溶出量が不足し、膜分離の透過水中のセレンとフッ素の濃度が十分に低下しないおそれがある。
【０００６】
本発明方法においては、凝集固液分離により、好ましくは懸濁物質濃度を３００mg／Ｌ以下とした水を、(Ｂ)酸性条件で鉄と接触させて鉄(II)イオンを溶出させる。水を酸性条件とする方法に特に制限はないが、塩酸、硫酸などの添加により、pH５以下に調整することが好ましく、pH２〜３に調整することがより好ましい。接触させる鉄に特に制限はなく、例えば、純鉄、粗鋼、合金鋼、その他の鉄合金などを挙げることができる。鉄は、鉄粒子、鉄網線などの表面積の大きい形状であることが好ましい。酸性条件に調整した水を鉄と接触させる方法に特に制限はなく、鉄金属粒子流動層に通水してもよいが、鉄金属充填層に通水することにより鉄と接触させることが好ましい。酸性条件に調整した水を鉄と接触させることにより、次式にしたがって鉄(II)イオンが溶出する。
Ｆｅ ＋ ２Ｈ+ → Ｆｅ2+ ＋ Ｈ2
このとき水素ガスが発生するので、鉄金属充填層に通水する場合は、上向流とすることが好ましい。水中の６価のセレンは、水中に溶出した鉄(II)イオンと次式にしたがって反応し、還元される。
ＳｅＯ4 2- ＋ ６Ｆｅ2+ ＋ ８Ｈ+ → Ｓｅ0 ＋ ６Ｆｅ3+ ＋ ４Ｈ2Ｏ
なお、セレンは微量であるため、鉄(II)イオンの大部分は鉄(III)イオンとならず残留する。
鉄(II)イオンが溶出し、６価のセレンが還元された水は、次いで(Ｃ)酸化剤と反応させる。使用する酸化剤に特に制限はなく、例えば、空気中の酸素ガス、過酸化水素などを挙げることができる。空気中の酸素ガスを酸化剤として利用する場合、水中の水酸化第一鉄は、次式にしたがって水酸化第二鉄を主体とする、中性条件でも溶解度の低い鉄化合物となる。被処理水がマンガンを含有する場合には、マンガンも不溶化される。
４Ｆｅ(ＯＨ)2 ＋ Ｏ2 ＋ ２Ｈ2Ｏ → ４Ｆｅ(ＯＨ)3
本反応はアルカリ性で促進されるので、鉄と接触させた後の水に必要に応じ、アルカリ剤を添加してpH６〜９、好ましくはpH７〜８.５に調整したのち酸化剤と反応させる。使用するアルカリ剤に特に制限はなく、例えば、水酸化ナトリウム、水酸化カリウム、消石灰、炭酸ナトリウム、炭酸カリウムなどを挙げることができる。
【０００７】
本発明方法においては、酸化剤との反応により水酸化第二鉄を析出させた水に、さらに(Ｄ)無機凝集剤を添加する。使用する無機凝集剤に特に制限はなく、例えば、塩化アルミニウム、ポリ塩化アルミニウム、硫酸アルミニウム、消石灰、水酸化マグネシウムなどを挙げることができる。これらの中で、塩化アルミニウム、ポリ塩化アルミニウム及び硫酸アルミニウムを好適に使用することができる。無機凝集剤の種類、量、(Ｃ)工程処理水質に応じ、アルカリ剤や、塩化カルシウムや、塩酸、硫酸などの酸剤を併用して、pH６〜８とすることが好ましく、pH６〜７とすることがより好ましい。本工程に用いる無機凝集剤は、最初の(Ａ)凝集固液分離に用いた凝集剤と、同一であっても異なっていてもよい。無機凝集剤を添加することにより、水酸化第二鉄は、中性条件のまま凝集してフロックを形成するとともに、還元されたセレン及び水中に残存するフッ素がフロックに吸着されて除去される。本発明方法においては、セレン、フッ素及びその他の懸濁物質を含有する水に、最初に(Ａ)凝集剤を添加して凝集固液分離し、水酸化第二鉄を析出させたのちに、さらに(Ｄ)無機凝集剤添加することにより、凝集剤の全使用量を低減することができる。
無機凝集剤を添加した水は、最後に(Ｅ)膜分離することにより、セレンとフッ素の濃度の十分に低い透過水を得ることができる。使用する分離膜に特に制限はなく、例えば、ポリアミド、酢酸セルロースなどの精密ろ過膜などを挙げることができる。本発明方法においては、膜分離に供する水のpHを６〜８とすることができるので、ろ過膜は耐アルカリ性である必要がなく、広い範囲のろ過膜から使用するろ過膜を選択することができる。また、中性条件で通水できるために、水酸化マグネシウムの沈着による膜フラックスの低下が起こりにくい。また、(Ｃ)、(Ｄ)、(Ｅ)の工程を一貫してpH６〜９で行うことができるため、pH調整剤の使用量を低減することができる。
【０００８】
図１は、本発明の水処理方法の実施の一態様の工程系統図である。セレン、フッ素及びその他の懸濁物質を含有する排煙脱硫排水を凝集槽１に送り込み、凝集剤とアルカリを添加する。懸濁物質が凝集した水を沈殿槽２へ送り、固液分離する。沈殿槽の上澄水は、酸を添加して酸性条件としたのち、鉄金属充填層３へ送り、鉄と接触させる。溶出した鉄(II)イオンが含まれる水は、酸化槽４へ送り、必要に応じてアルカリを添加してpH６〜９、好ましくはpH７〜８.５に調整し、酸化剤として空気を送り込んで曝気し、鉄(II)イオンを水酸化第二鉄に変換して析出させる。曝気の代わりに、過酸化水素などの酸化剤を添加することもできる。水酸化第二鉄が析出した水は、凝集槽５に送り、無機凝集剤を添加して、pH６〜８、好ましくはpH６〜７において水酸化第二鉄の凝集フロックを形成させるとともに、還元されたセレンと水中に残存するフッ素をフロックに吸着させる。水酸化第二鉄の凝集フロックが形成された水は、膜分離装置６に送って膜分離し、透過水を処理水として得る。
従来の方法では、石炭火力発電所の排煙脱硫排水などの高濃度の懸濁物質を含む排水は、鉄金属充填層の詰まりを生じて通水が困難となるのみならず、酸性条件とすることにより溶解した懸濁物質が、鉄金属充填層への通水によりpH５〜６となると鉄表面に再析出して還元反応を阻害する。本発明方法によれば、セレン、フッ素及びその他の懸濁物質を含む水に、最初に(Ａ)凝集剤を添加して凝集固液分離するので、鉄金属充填層の詰まりや、鉄金属の表面汚れを生ずるおそれがない。また、従来の方法では、溶出した鉄(II)イオンは、水のpHを９以上に調整することにより水酸化第一鉄として沈殿させ、セレンとともに除去していた。しかし、排煙脱硫排水の処理で主流となっている膜分離装置では、pH９以上では同時に析出する水酸化マグネシウムが膜フラックスを低下させるために、通液が困難となる。本発明方法によれば、酸化剤と反応させ、鉄(II)イオンを酸化して水酸化第二鉄として析出させ、pH６〜８というほぼ中性条件で膜分離することにより、膜フラックスの低下を防ぐことができる。
【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
図１に示す工程により、排煙脱硫排水の処理を行った。
懸濁物質７１０mg／Ｌ、セレン(VI)０.５mg／Ｌ及びフッ素２００mg／Ｌを含む石炭火力発電所の排煙脱硫排水に、ポリ塩化アルミニウム６,４００mg／Ｌと水酸化ナトリウムを添加してpH６.０〜６.５とし凝集沈殿処理した。凝集沈殿処理後の上澄水の水質は、懸濁物質２０mg／Ｌ、セレン０.５mg／Ｌ及びフッ素３０mg／Ｌであった。
この上澄水に、塩酸を塩化水素として６５０mg／Ｌ添加し、酸性に調整したのち、平均粒径が０.３mmで、９０重量％以上が粒径０.１８〜０.５mmである球状鉄金属粒子１.６リットルを充填した鉄金属充填層に、４５Ｌ／hr（ＬＶ４０ｍ／hr）で上向流で通水した。鉄金属充填層流出水には、鉄４２０mg／Ｌが溶出していた。
鉄金属充填層流出水を酸化槽へ導き、水酸化ナトリウムを添加してpH７.６〜８.０に調整するとともに、空気量９００Ｌ／hr、滞留時間３.５hrで曝気処理した。
曝気処理後の水に、ポリ塩化アルミニウム１,２００mg／Ｌを添加したところ、pH６〜７であった。これを孔径０.２μｍ、膜面積０.０３６ｍ2の精密ろ過膜を内装した膜分離装置に、実フラックス１０ｍ／ｄの運転条件で通水した。膜分離装置透過水の水質は、セレン０.０３mg／Ｌ、フッ素８.０mg／Ｌであった。１０日間運転を続けたところ、この間の基準フラックスの低下速度は０.２〜０.４ｍ／ｄ／ｄであった。
比較例１
図２に示す工程により、排煙脱硫排水の処理を行った。
実施例１と同じ排煙脱硫排水に、塩酸を塩化水素として６５０mg／Ｌ添加して酸性に調整したのち、実施例１と同じ鉄金属充填層３に、４５Ｌ／hr（ＬＶ４０ｍ／hr）で上向流で通水した。鉄金属充填層流出水には、鉄１８０mg／Ｌが溶出していた。
鉄金属充填層流出水を酸化槽４へ導き、水酸化ナトリウムを添加してpH７.６〜８.０に調整するとともに、空気量９００Ｌ／hr、滞留時間３.５hrで曝気処理した。
曝気処理後の水を凝集槽５に導き、ポリ塩化アルミニウム１２,６００mg／Ｌを添加し、水酸化ナトリウムを加えてpH６〜７に調整したのち、実施例１と同じ膜分離装置６に、実フラックス１０ｍ／ｄの運転条件で通水した。膜分離装置透過水の水質は、セレン０.３２mg／Ｌ、フッ素８.４mg／Ｌであった。１０日間運転を続けたところ、この間の基準フラックスの低下速度は０.２〜０.４ｍ／ｄ／ｄであった。
比較例２
ポリ塩化アルミニウムの添加量を７,６００mg／Ｌとした以外は、比較例１と同じ操作を行った。
膜分離装置透過水の水質は、セレン０.３３mg／Ｌ、フッ素２２mg／Ｌであった。１０日間運転を続けたところ、この間の基準フラックスの低下速度は０.２〜０.４ｍ／ｄ／ｄであった。
比較例３
図３に示す工程により、排煙脱硫排水の処理を行った。
実施例１と同じ排煙脱硫排水に、ポリ塩化アルミニウム７,６００mg／Ｌを添加し、水酸化ナトリウムによりpH６.０〜６.５に調整して凝集沈殿処理した。凝集沈殿処理後の上澄水の水質は、懸濁物質２２mg／Ｌ、セレン０.５mg／Ｌ及びフッ素２３mg／Ｌであった。
この上澄水に、塩酸を塩化水素として６５０mg／Ｌ添加し、酸性に調整したのち、実施例１と同じ鉄金属充填層３に、４５Ｌ／hr（ＬＶ４０ｍ／hr）で上向流で通水した。鉄金属充填層流出水には、鉄４２０mg／Ｌが溶出していた。
鉄金属充填層流出水をpH調整槽７に導き、水酸化ナトリウムを添加してpH９.５に調整し、実施例１と同じ膜分離装置６に、実フラックス１０ｍ／ｄの運転条件で通水した。膜分離装置透過水の水質は、セレン０.０３mg／Ｌ、フッ素１６mg／Ｌであった。３日間運転を続けたところ、この間の基準フラックスの低下速度は１.０〜２.０ｍ／ｄ／ｄであった。
実施例１及び比較例１〜３の結果を、第１表に示す。
【００１０】
【表１】
第１表に見られるように、最初に(Ａ)ポリ塩化アルミニウムを添加して凝集固液分離し、(Ｂ)酸性条件で鉄充填層に通水して鉄(II)イオンを溶出させたのち、(Ｃ)pH７.６〜８.０に調整して曝気処理して水酸化第二鉄を析出させ、さらに(Ｄ)ポリ塩化アルミニウムを添加し、pH６〜７として(Ｅ)精密ろ過膜を用いて膜分離した実施例１においては、セレンとフッ素が低濃度まで除去され、基準フラックスの低下速度も小さく、安定して効率的にセレン、フッ素及びその他の懸濁物質を含有する排水を処理し得ることが分かる。
これに対して、最初の(Ａ)凝集固液分離処理を行わない比較例１では、鉄(II)イオンの溶出量が少なく、ポリ塩化アルミニウムの全使用量を増しても、セレンを十分に低濃度にすることができない。また、ポリ塩化アルミニウムの全使用量を実施例１と同量まで減じた比較例２においては、処理水中のフッ素濃度も上昇する。また、溶出した鉄(II)イオンを、水をpH９.５に調整することにより、水酸化第一鉄として析出させた比較例３では、基準フラックスの低下が速く、安定して処理を継続することができない。
【００１２】
【発明の効果】
本発明の水処理方法によれば、最初に凝集剤を添加して凝集固液分離することにより、鉄と接触させる工程における還元性能の低下を防止することができ、鉄と接触させ、さらに酸化剤と反応させたのち、無機凝集剤を用いることにより、少量の凝集剤でフッ素除去を確実に行うとともに、中性条件で膜分離することができ、膜フラックスの低下が小さくなり、良好な膜分離を行うことができる。また、酸化剤との反応、凝集、膜分離を一貫してpH６〜９で行うことができるため、pH調整剤の使用量も低減される。
【図面の簡単な説明】
【図１】図１は、本発明の水処理方法の実施の一態様の工程系統図である。
【図２】図２は、比較例１及び比較例２において用いた工程系統図である。
【図３】図３は、比較例３において用いた工程系統図である。
【符号の説明】
１ 凝集槽
２ 沈殿槽
３ 鉄金属充填層
４ 酸化槽
５ 凝集槽
６ 膜分離装置
７ pH調整槽[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water treatment method. More specifically, the present invention treats wastewater containing selenium, fluorine, and suspended solids, such as flue gas desulfurization effluent from coal-fired power plants, by membrane separation so that there is little decrease in membrane flux and selenium and fluorine are treated. The present invention relates to a water treatment method that can be efficiently removed.
[0002]
[Prior art]
Flue gas desulfurization effluent generated in coal-fired power plants and the like contains harmful substances such as selenium and fluorine in addition to suspended substances. Therefore, it is necessary to remove these substances by water treatment. The selenium in the waste water usually exists as colloidal selenium, tetravalent selenite ion (SeO 3 2− ) or hexavalent selenate ion (SeO 4 2− ). Among these, since removal of hexavalent selenate ions is particularly difficult, various water treatment methods have been proposed.
For example, in JP-A-9-187778, as a method for efficiently treating wastewater containing toxic substances such as selenium and fluorine discharged from a flue gas desulfurization apparatus, the pH of the flue gas desulfurization waste water is adjusted to 5 or less. Then, after making it contact with iron, the processing method of the flue gas desulfurization waste water which performs a coagulation process and solid-liquid separation is proposed. However, in this method, the amount of flocculant required to remove fluorine is large, and when membrane separation is used as the solid-liquid separation method, the water to be treated is made alkaline in the aggregation treatment. There is a problem that the scale is attached and the flux is lowered. Japanese Patent Application Laid-Open No. 11-28475 discloses a treatment method capable of efficiently removing the selenium concentration in the treated water down to 0.1 mg / L, which is a wastewater standard, and contacting the selenium-containing water with iron under acidic conditions. A method for treating selenium-containing water, comprising: a step of treating the selenium water, adjusting the pH of the treated water to be substantially neutral and then bringing it into contact with a peroxide; and a step of membrane separation after aggregation with a polymer flocculant. Proposed. However, this method cannot sufficiently remove the fluorine in the wastewater, so that if the wastewater contains fluorine, it is necessary to install a fluorine adsorption tower in the subsequent stage. Furthermore, it has been clarified that when the selenium-containing wastewater containing a large amount of suspended matter is passed through the iron metal particle layer as it is and the selenium in the wastewater is reduced, the reduction performance of the iron metal particles decreases.
For this reason, there has been a demand for a water treatment method that can efficiently remove these substances from waste water containing harmful substances such as selenium and fluorine and suspended substances, and that reduces the decrease in flux of the separation membrane. .
[0003]
[Problems to be solved by the invention]
The present invention treats wastewater containing selenium, fluorine, and suspended solids, such as flue gas desulfurization wastewater from coal-fired power plants, by membrane separation to reduce membrane flux and efficiently remove selenium and fluorine. It was made for the purpose of providing a possible water treatment method.
[0004]
[Means for Solving the Problems]
As a result of intensive research to solve the above-mentioned problems, the present inventors conducted flocculation solid-liquid separation of water containing selenium and fluorine, and after removing most of the fluorine, contacted with iron under acidic conditions. By eluting iron (II) ions, reacting with an oxidant to precipitate ferric hydroxide, adding an inorganic flocculant, and then separating the membrane, the membrane flux is less reduced and selenium and fluorine are more efficient. Based on this finding, the present invention has been completed.
That is, the present invention
(1) water containing selenium and fluorine, to obtain (A) agglomerated solid-liquid separation by adding a coagulant, water after separation of the suspended matter concentration below 300 mg / L, (B) the After the separated water is brought into contact with iron under acidic conditions to elute iron (II) ions, (C) ferric hydroxide is precipitated by reacting with an oxidizing agent, and (D) inorganic flocculant Water treatment method characterized by adding (E) membrane separation,
(2) The water treatment method according to item (1), wherein the oxidizing agent is air, and
(3) The water treatment method according to item (1) or (2), wherein (D) the inorganic flocculant is polyaluminum chloride,
Is to provide.
Furthermore, as a preferred embodiment of the present invention,
( 4 ) The water treatment method according to item (1), wherein the water containing selenium and fluorine further contains suspended solids.
( 5 ) The water treatment method according to ( 4 ), wherein the water containing selenium, fluorine and suspended solids is flue gas desulfurization effluent from a coal-fired power plant,
( 6 ) (B) The water treatment method according to item (1), wherein the contact with iron is performed by passing water through an iron metal packed bed;
( 7 ) (C) The water treatment method according to item (1), wherein the reaction with the oxidizing agent is performed at
( 8 ) (D) The water treatment method according to item (1), wherein an inorganic flocculant is added and the aggregation reaction is performed at
Can be mentioned.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In the water treatment method of the present invention, water containing selenium and fluorine is (A) agglomerated by adding a coagulant, and (B) contacting iron under acidic conditions to elute iron (II) ions. Then, (C) ferric hydroxide is precipitated by reacting with an oxidizing agent, (D) an inorganic flocculant is added, and (E) membrane separation is performed. The method of the present invention can be suitably applied to the treatment of flue gas desulfurization effluent from a coal-fired power plant.
In the method of the present invention, (A) a flocculant is added to water containing selenium and fluorine to perform agglomeration solid-liquid separation. There is no particular limitation on the flocculant used, for example, sulfuric acid band, polyaluminum chloride, ferrous sulfate, ferric chloride, slaked lime, magnesium hydroxide and other inorganic flocculants, sodium alginate, carboxymethylcellulose, polyacrylamide Anionic polymer flocculants such as hydrolyzate salts, cationic polymer flocculants such as polyethyleneimine, polythiourea and quaternary ammonium salts, and nonionic polymer flocculants such as polyacrylamide . In particular, an inorganic flocculant having high fluorine removal performance is preferred. These flocculants can be used individually by 1 type, or can also be used in combination of 2 or more type. By adding a flocculant to water containing selenium and fluorine, most of the suspended substance aggregates to form a floc, and fluorine in the water is adsorbed and removed by the floc. The method for separating and removing the aggregated floc is not particularly limited, and examples thereof include precipitation, levitation, centrifugation, and cyclone.
In the method of the present invention, since (D) a post-process of adding an inorganic flocculant is included, there is no problem even if fluorine and part of the suspended solids remain in the first (A) flocculent solid-liquid separation. . Therefore, it is not necessary to highly remove the aggregated flocs, and simple equipment can be used. By removing suspended substances first, when adjusting to (B) acidic conditions, the amount of acid consumed to dissolve suspended substances is reduced, and water treatment can be carried out economically. . The concentration of the suspended substance in water after the flocculated solid-liquid separation is preferably 300 mg / L or less, and more preferably 100 mg / L or less. When the concentration of suspended solids in water after flocculated solid-liquid separation exceeds 300 mg / L, the elution of iron is inhibited and the elution amount of iron (II) ions is insufficient in contact with iron under acidic conditions (B) However, the concentration of selenium and fluorine in the permeated water for membrane separation may not be sufficiently reduced.
[0006]
In the method of the present invention, water with a suspended solid concentration of preferably 300 mg / L or less is brought into contact with iron under acidic conditions (B) by flocculation solid-liquid separation to elute iron (II) ions. Although there is no restriction | limiting in particular in the method of making water into acidic conditions, It is preferable to adjust to pH 5 or less by addition of hydrochloric acid, a sulfuric acid, etc., and it is more preferable to adjust to pH 2-3. There is no restriction | limiting in particular in the iron made to contact, For example, pure iron, crude steel, alloy steel, other iron alloys etc. can be mentioned. The iron is preferably in a shape having a large surface area such as iron particles and iron wire. There is no restriction | limiting in particular in the method of making the water adjusted to acidic conditions contact with iron, Although water may be passed through an iron metal particle fluidized bed, it is preferable to contact with iron by passing through an iron metal packed bed. When water adjusted to acidic conditions is brought into contact with iron, iron (II) ions are eluted according to the following formula.
Fe + 2H + → Fe 2+ + H 2
Since hydrogen gas is generated at this time, it is preferable that the water flow upward when flowing through the iron metal packed bed. Hexavalent selenium in water reacts with iron (II) ions eluted in water according to the following formula and is reduced.
SeO 4 2- + 6Fe 2+ + 8H + → Se 0 + 6Fe 3+ + 4H 2 O
Since selenium is a trace amount, most of the iron (II) ions remain as iron (III) ions.
The water from which iron (II) ions are eluted and hexavalent selenium is reduced is then reacted with (C) an oxidizing agent. There is no restriction | limiting in particular in the oxidizing agent to be used, For example, the oxygen gas in air, hydrogen peroxide, etc. can be mentioned. When oxygen gas in the air is used as an oxidizing agent, ferrous hydroxide in water becomes an iron compound having a low solubility even under neutral conditions, mainly ferric hydroxide according to the following formula. When the water to be treated contains manganese, manganese is also insolubilized.
4Fe (OH) 2 + O 2 + 2H 2 O → 4Fe (OH) 3
Since this reaction is promoted by alkalinity, an alkali agent is added to water after being brought into contact with iron, if necessary, and adjusted to
[0007]
In the method of the present invention, (D) an inorganic flocculant is further added to water in which ferric hydroxide is precipitated by reaction with an oxidizing agent. There is no restriction | limiting in particular in the inorganic flocculant to be used, For example, aluminum chloride, polyaluminum chloride, aluminum sulfate, slaked lime, magnesium hydroxide etc. can be mentioned. Among these, aluminum chloride, polyaluminum chloride and aluminum sulfate can be preferably used. According to the type and amount of the inorganic flocculant, and (C) process water quality, it is preferable to adjust the pH to 6-8 by using an alkaline agent, an acid agent such as calcium chloride, hydrochloric acid, sulfuric acid, etc. More preferably. The inorganic flocculant used in this step may be the same as or different from the flocculant used for the initial (A) flocculation solid-liquid separation. By adding an inorganic flocculant, ferric hydroxide aggregates to form flocs under neutral conditions, and reduced selenium and fluorine remaining in water are adsorbed and removed by the flocs. In the method of the present invention, (A) a flocculant is first added to water containing selenium, fluorine, and other suspended solids, and after agglomerated solid-liquid separation to precipitate ferric hydroxide, Furthermore, the total amount of the flocculant used can be reduced by adding (D) an inorganic flocculant.
The water to which the inorganic flocculant is added is finally (E) membrane-separated to obtain permeated water having a sufficiently low concentration of selenium and fluorine. There is no restriction | limiting in particular in the separation membrane to be used, For example, microfiltration membranes, such as a polyamide and a cellulose acetate, etc. can be mentioned. In the method of the present invention, the pH of water used for membrane separation can be adjusted to 6-8, so the filtration membrane does not need to be alkali resistant, and a filtration membrane to be used can be selected from a wide range of filtration membranes. it can. Moreover, since water can be passed under neutral conditions, the membrane flux is not easily lowered by the deposition of magnesium hydroxide. Moreover, since the steps (C), (D), and (E) can be performed consistently at
[0008]
FIG. 1 is a process flow diagram of one embodiment of the water treatment method of the present invention. The flue gas desulfurization waste water containing selenium, fluorine and other suspended substances is sent to the coagulation tank 1, and the coagulant and alkali are added. The water in which the suspended substance is agglomerated is sent to the precipitation tank 2 for solid-liquid separation. The supernatant water of the precipitation tank is acidified by adding an acid, and then sent to the iron metal packed bed 3 to be brought into contact with iron. The water containing the eluted iron (II) ions is sent to the
In conventional methods, wastewater containing high-concentration suspended solids such as flue gas desulfurization wastewater from coal-fired power plants not only causes clogging of the iron metal packed bed and makes it difficult to pass water, but also makes it acidic conditions. When the suspended substance dissolved thereby reaches pH 5-6 by passing water through the iron metal packed bed, it reprecipitates on the iron surface and inhibits the reduction reaction. According to the method of the present invention, since (A) the flocculant is first added to the water containing selenium, fluorine and other suspended solids, the solidified solid-liquid separation is performed. There is no risk of surface contamination. In the conventional method, the eluted iron (II) ions are precipitated as ferrous hydroxide by adjusting the pH of the water to 9 or more and removed together with selenium. However, in a membrane separation apparatus that is mainstream in the treatment of flue gas desulfurization wastewater, magnesium hydroxide that precipitates simultaneously at a pH of 9 or more reduces the membrane flux, making it difficult to pass liquid. According to the method of the present invention, the membrane flux is decreased by reacting with an oxidizing agent, oxidizing iron (II) ions to precipitate as ferric hydroxide, and performing membrane separation under substantially neutral conditions of pH 6-8. Can be prevented.
[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
The flue gas desulfurization waste water was treated by the process shown in FIG.
To a flue gas desulfurization effluent of a coal-fired power plant containing 710 mg / L of suspended solids, 0.5 mg / L of selenium (VI) and 200 mg / L of fluorine, polyaluminum chloride 6,400 mg / L and sodium hydroxide were added. The pH was adjusted to 6.0 to 6.5 and the coagulation precipitation treatment was performed. The water quality of the supernatant water after the coagulation sedimentation treatment was 20 mg / L of suspended solids, 0.5 mg / L of selenium and 30 mg / L of fluorine.
To this supernatant water, 650 mg / L of hydrochloric acid as hydrogen chloride was added to adjust the acidity, and then the spherical iron metal having an average particle diameter of 0.3 mm and 90% by weight or more having a particle diameter of 0.18 to 0.5 mm. Water was passed in an upward flow at 45 L / hr (LV 40 m / hr) through an iron metal packed bed filled with 1.6 liters of particles. In the iron metal packed bed effluent, 420 mg / L of iron was eluted.
The iron metal packed bed effluent was introduced into an oxidation tank, sodium hydroxide was added to adjust the pH to 7.6 to 8.0, and aeration treatment was performed at an air amount of 900 L / hr and a residence time of 3.5 hr.
When 1,200 mg / L of polyaluminum chloride was added to the water after the aeration treatment, the pH was 6-7. This was passed through a membrane separation apparatus equipped with a microfiltration membrane having a pore diameter of 0.2 μm and a membrane area of 0.036 m 2 under operating conditions of an actual flux of 10 m / d. The water quality of the permeated water of the membrane separator was 0.03 mg / L selenium and 8.0 mg / L fluorine. When the operation was continued for 10 days, the decrease rate of the reference flux during this period was 0.2 to 0.4 m / d / d.
Comparative Example 1
The flue gas desulfurization waste water was treated by the process shown in FIG.
After adding 650 mg / L of hydrochloric acid as hydrogen chloride to the same flue gas desulfurization effluent as in Example 1, it was adjusted to acidity, and the same was added to the same iron metal packed bed 3 as in Example 1 at 45 L / hr (LV 40 m / hr). Water flowed in a countercurrent. In the iron metal packed bed effluent, 180 mg / L of iron was eluted.
The iron metal packed bed effluent was led to the
After the aeration treatment, the water is introduced into the coagulation tank 5, 12,600 mg / L of polyaluminum chloride is added, and sodium hydroxide is added to adjust the pH to 6-7. Water was passed under operating conditions with a flux of 10 m / d. The water quality of the permeated water of the membrane separator was 0.32 mg / L selenium and 8.4 mg / L fluorine. When the operation was continued for 10 days, the decrease rate of the reference flux during this period was 0.2 to 0.4 m / d / d.
Comparative Example 2
The same operation as in Comparative Example 1 was performed except that the amount of polyaluminum chloride added was 7,600 mg / L.
The water quality of the permeated water of the membrane separator was 0.33 mg / L selenium and 22 mg / L fluorine. When the operation was continued for 10 days, the decrease rate of the reference flux during this period was 0.2 to 0.4 m / d / d.
Comparative Example 3
The exhaust gas desulfurization waste water was treated by the process shown in FIG.
To the same flue gas desulfurization effluent as in Example 1, 7,600 mg / L of polyaluminum chloride was added, adjusted to pH 6.0 to 6.5 with sodium hydroxide, and coagulated and precipitated. The quality of the supernatant water after the coagulation sedimentation treatment was 22 mg / L of suspended solids, 0.5 mg / L of selenium and 23 mg / L of fluorine.
To this supernatant water, 650 mg / L of hydrochloric acid as hydrogen chloride was added to adjust the acidity, and then water was passed upwardly at 45 L / hr (LV 40 m / hr) through the same iron metal packed bed 3 as in Example 1. . In the iron metal packed bed effluent, 420 mg / L of iron was eluted.
The iron metal packed bed effluent is led to the
The results of Example 1 and Comparative Examples 1 to 3 are shown in Table 1.
[0010]
[Table 1]
As can be seen in Table 1, first (A) polyaluminum chloride was added to separate the agglomerated solid and liquid, and (B) water was passed through the iron packed bed under acidic conditions to elute iron (II) ions. Then, (C) pH 7.6 to 8.0 is adjusted and aerated to precipitate ferric hydroxide, and (D) polyaluminum chloride is added to adjust
In contrast, in Comparative Example 1 in which the first (A) aggregation solid-liquid separation treatment is not performed, the amount of iron (II) ions eluted is small, and even when the total amount of polyaluminum chloride is increased, selenium is sufficiently obtained. The concentration cannot be reduced. Moreover, in the comparative example 2 which reduced the total usage-amount of polyaluminum chloride to the same amount as Example 1, the fluorine concentration in treated water also rises. Further, in Comparative Example 3 in which the eluted iron (II) ions were precipitated as ferrous hydroxide by adjusting water to pH 9.5, the reference flux decreased rapidly and the treatment was continued stably. I can't.
[0012]
【The invention's effect】
According to the water treatment method of the present invention, by first adding a flocculant and performing agglomeration solid-liquid separation, it is possible to prevent reduction in reduction performance in the step of contacting with iron. After reacting with the agent, by using an inorganic flocculant, fluorine removal can be reliably performed with a small amount of flocculant, and membrane separation can be performed under neutral conditions. Separation can be performed. In addition, since the reaction with the oxidizing agent, aggregation, and membrane separation can be performed consistently at
[Brief description of the drawings]
FIG. 1 is a process flow diagram of one embodiment of a water treatment method of the present invention.
FIG. 2 is a process flow diagram used in Comparative Example 1 and Comparative Example 2;
FIG. 3 is a process flow diagram used in Comparative Example 3;
[Explanation of symbols]
1 Coagulation tank 2 Precipitation tank 3 Iron metal packed
Claims (3)
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| JP4827541B2 (en) * | 2005-01-31 | 2011-11-30 | 株式会社 イージーエス | Immobilizing agent for harmful components and immobilizing method |
| JP5261950B2 (en) * | 2006-07-04 | 2013-08-14 | 栗田工業株式会社 | Method and apparatus for treating selenium-containing wastewater |
| JP5106463B2 (en) * | 2009-03-30 | 2012-12-26 | 太平洋セメント株式会社 | Method and apparatus for processing solution containing selenium and fluorine |
| JP5170461B2 (en) * | 2009-08-31 | 2013-03-27 | 三菱マテリアル株式会社 | Treatment of selenium-containing wastewater |
| JP5579414B2 (en) * | 2009-09-30 | 2014-08-27 | 千代田化工建設株式会社 | Treatment method for wastewater containing reducing selenium |
| KR101957548B1 (en) * | 2012-11-30 | 2019-03-12 | 오르가노 코포레이션 | System for treating coal gasification wastewater, and method for treating coal gasification wastewater |
| CN106219816B (en) * | 2016-08-25 | 2019-04-23 | 万华化学集团股份有限公司 | A kind of treatment method of reverse osmosis concentrated water |
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