PURPOSE: To effectively decolorize a pulp and paper making waste water by treating the waste water with a reducing agent which can at least partly deactivate the functional groups which give a color to the waste water, and then treating the waste water with a polymer which can decolorize the waste water.
CONSTITUTION: When a pulp and paper making waste water is to be decolorized, first, the waste water is treated with a reducing agent which can at least partly deactivate the functional groups which give a color to the waste water. Then the waste water is treated with a polymer which can decolorize the waste water. Preferably, the reducing agent used at least partly deactivates color- developing functional groups by oxidation, reduction and/or chemical modification, and for example, a sodium hydrogen sulfite, hydrosulfite, sodium persulfate or the like can be used. As for the polymer, polyamine, preferably epichlorohydrin-dimethylamine is used. The waste water is treated in about 4.0 to about 11.0 pH range.
EIMII EMU TSUEN
JIYON EICHI KORINZU
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