METHOD FOR TREATING DUST-COLLECTED WATER

To provide a method for effectively removing cyanide components without requiring an additional sedimentation tank after solid-liquid separation of suspended matter in dust-collected water by a solid-liquid separation facility.SOLUTION: A method is to treat dust-collected water using a solid-liquid separation apparatus 40 for solid-liquid separation of suspended matter in the dust-collected water obtained by a wet dust collection treatment of exhaust gas, and a circulation apparatus 50 in which a part of the separation liquid is used as washing water for the wet dust collection treatment. The dust-collected water additionally contains cyanide ions and pentacyanocarbonyl iron complexes. Under conditions satisfying at least one of condition 1 in which the suspended substance in the dust-collected water contains one or both of zinc and copper, and condition 2 in which a zinc salt is additionally added to the dust-collected water, the method includes: adding a cationic compound having an amine structure to the dust-collected water for subjecting it to solid-liquid separation treatment in the solid-liquid separation apparatus; and discharging a part of the separation liquid obtained by the solid-liquid separation treatment to outside of the circulation apparatus as blown water separately from the washing water used for the wet dust collection treatment, and adding an oxidizing agent to the blown water for treatment.SELECTED DRAWING: Figure 1 【課題】集塵水中の懸濁物質を固液分離設備にて固液分離した後にさらなる沈殿槽を必要とせずに、シアン成分を有効に除去処理する方法の提供。【解決手段】排ガスの湿式集塵処理により得られる集塵水中の懸濁物質を固液分離する固液分離設備４０と、得られた分離液の一部を洗浄水として湿式集塵処理に供する循環設備５０とを用いて集塵水を処理する。集塵水はさらにシアン化物イオン及びペンタシアノカルボニル鉄錯体を含有する。集塵水中の懸濁物質が亜鉛及び銅の一方又は両方を含む条件１、及び集塵水にさらに亜鉛塩を添加する条件２のうちの少なくとも一方を満たす条件下、集塵水にアミン構造を有するカチオン性化合物を添加して固液分離設備で固液分離処理すること；並びに固液分離処理により得られた分離液の一部を湿式集塵処理に供する洗浄水とは別にブロー水として循環設備外に排出し、ブロー水に対して酸化剤を添加して処理すること；を含む。【選択図】図１