Method of treating waste water to remove harmful ion by coagulating sedimentation

Abstract

The invention relates to the treatment of waste water containing a harmful ion such as a heavy metal ion or fluorine ion by the coagulating sedimentation method using an inorganic coagulant such as an iron compound or an aluminum compound. After separating treated water from the sediment (sludge) in which the harmful ion is incorporated in insoluble form, the pH of a mixture of the sediment and water is suitably adjusted to cause elution of the harmful ion from the sediment. Then the sediment is separated from the eluate and reused as an inorganic coagulant. By reusing the sediment in this manner, the waste water treatment is accomplished without producing a large quantity of sludge and the consumption of inorganic coagulant and auxiliary chemicals can be greatly reduced, while the concentration of the harmful ion in the treated water becomes sufficiently low.

Dependencies are inferred from the claim text.