PROCESSING METHOD OF HEAVY METAL-CONTAINING WASTE WATER

To provide a processing method capable of stably separating and removing heavy metal even from waste water whose concentration of the heavy metal greatly varies.SOLUTION: A processing method of heavy metal-containing waste water of this invention includes: a step of desalting and cleaning chlorine-containing ash; a sulfurizing step of adding a sulfurizing agent to the cleaned waste water obtained by solid-liquid separating the desalted/cleaned slurry to cause heavy metal sulfide to be precipitated; and a step of solid-liquid separating the precipitated heavy metal sulfide. In the desalting and cleaning step, cleaning is performed by controlling conductivity of the cleaned slurry to be 5.0 S/m or lower. And the processing method includes a step of: after the sulfurizing step, causing residual sulfide ions to be turned into sulfide iron to be precipitated by adding a ferrous compound to the cleaned waste water; further causing residual ferrous ions to be turned into iron hydroxide to be precipitated by pH adjustment, and solid-liquid separating the precipitant. The processing method includes, after the solid-liquid separating step, an ORP adjusting step of adjusting, by adding an oxidation agent to the separated liquid content, an oxidation-reduction potential of the liquid content to 50-350 mv in terms of a silver chloride electrode.SELECTED DRAWING: Figure 1 【課題】重金属濃度が大きく変動する廃水からでも、これらの重金属を安定に分離除去することができる処理方法を提供する。【解決手段】塩素含有灰を脱塩洗浄する工程、脱塩洗浄スラリーを固液分離した洗浄廃水に硫化剤を添加して重金属の硫化物を沈澱させる硫化工程、該重金属硫化物沈澱を固液分離する工程を有し、脱塩洗浄工程において、洗浄スラリーの電気伝導度を５.０S/ｍ以下に制御して洗浄を行い、硫化工程の後に、該洗浄廃水に第一鉄化合物を添加して残留硫化物イオンを硫化鉄にして沈澱させ、さらにｐＨ調整して残留第一鉄イオンを水酸化鉄にして沈澱させた後に、上記沈澱を固液分離する工程を有し、上記固液分離工程の後に、分離した液分に酸化剤を添加して該液分の酸化還元電位を塩化銀電極基準として５０mV〜３５０mVに調整するＯＲＰ調整工程を有することを特徴とする重金属含有廃水の処理方法。【選択図】図１