TREATMENT OF WASTE WATER

摘要

PROBLEM TO BE SOLVED: To easily remove selenium, etc., by executing sedimentation after forming a flocculated flock by adding aluminum salt to a waste water and adding a liquid chelating agent to its supernatant liq., and adding the aluminum salt to its reacted liq. to flocculate a solid matter at the time of treating the waste water containing selenium, etc. SOLUTION: At the time of treating a desulfurized waste water 21 discharged from a flue gas desulfurizer and containing a fluorine compd., at first the flocculated flock is forming by introducing the desulfurized waste water 21 to a pH adjusting tank 1 and adding the aluminum salt 22a and an alkali agent 23a, then a suspension containing the flocculated matter is introduced to a flocculating tank 2 to form a coarse flock by mixing with an org. high molecular flocculating agent 24a, then the suspension is introduced to a sedimentation tank 3 to execute solid liq. separation. Then the supernatant liq. 25 after solid- liq. separation is introduced to a reactor 4 to mix with the liquid chelating agent 26, and a trace heavy metals remained in the supernatant liq. 25 are insolubilized to form a microflock. Then the aluminum salt 22b is added to the reacted liq. in the reactor 4 to flocculate the flock and the flock is subjected to the solid-liq. separation in the flocculating tank 6.