RAW WATER TREATMENT METHOD

• Main Authors: MIMURA HITOSHI, OIWA TADAO, CAI HUILANG, MAEDA SHUNSUKE, YANAGIMOTO YOICHI
• Format: Patent
• Language: English; Japanese
• Published: 20.04.2017
• Subjects: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOIDCHEMISTRY; CHEMISTRY; METALLURGY; MIXING, e.g. DISSOLVING, EMULSIFYING, DISPERSING; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; THEIR RELEVANT APPARATUS; TRANSPORTING; TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

PROBLEM TO BE SOLVED: To provide a raw water treatment method capable of greatly reducing the disposal amount of an additive while efficiently improving the trapping efficiency of arsenic in raw water to greatly suppress an increase in running cost due to the additive.SOLUTION: Raw water G containing arsenic in an amount exceeding an environmental standard value is charged into a treatment tank 11 filled with granular carriers 10 and is treated at a flow rate that makes it impossible to produce a suspension of ferric hydroxide in the raw water while adding an acidic iron solution to the raw water G in the treatment tank 11 so as to adjust the pH value of the raw water G to 6.5-7.5. The catalytic oxidation reaction of soluble ferrous ions in the raw water G whose pH value has been adjusted produces a ferric hydroxide film on the entire surface of the carriers 10, and the arsenic in the raw water G is adsorbed on the ferric hydroxide. At this time, the ferric hydroxide film on the surface of the carriers 10 serves as a catalyst to accelerate the catalytic oxidation reaction of the soluble ferrous ion, thereby reliably trapping arsenic in the produced ferric hydroxide.SELECTED DRAWING: Figure 1 【課題】原水中のヒ素の捕獲効率を効果的に向上させ、添加剤によるランニングコストの高騰を大幅に抑制しつつ、添加剤の廃棄量も大幅に削減できる原水の処理方法を提供する。【解決手段】環境基準値を超えるヒ素が含有されている原水Ｇを、内部に粒状の担体１０が充填された処理槽１１に投入し、その原水ＧのｐＨ値を６．５〜７．５に調整するように、処理槽１１の原水Ｇに対し酸性の鉄溶液を添加しつつ、原水中に水酸化第二鉄の懸濁体を生成不能とする流速で処理する。ｐＨ値を調整した原水Ｇ中の溶解性第一鉄イオンを接触酸化反応により担体１０の表面全域に水酸化第二鉄皮膜として生成し、水酸化第二鉄に原水Ｇ中のヒ素を吸着させる。このとき、担体１０表面の水酸化第二鉄皮膜が触媒となって、溶解性第一鉄イオンの接触酸化反応が促進され、形成された水酸化第二鉄にヒ素を確実に捕獲する。【選択図】図１