To provide a treatment method eliminating the increase in cost due to the use of a condensation type polyamine in the treatment of used paper manufacturing wastewater and capable of efficiently performing the solid-liquid separation of used paper manufacturing wastewater even if a dissolved or suspended component is present in high concentration by using a polymeric flocculant of which the dissolution is completed in a short time.
A cationic and/or amphoteric water soluble polymer, which comprises a dispersion of fine particles with a particle size of 100 μm or less manufactured in a salt aqueous solution in the coexistence of a polymeric dispersant soluble in the salt aqueous solution by a dispersion polymerization method, is added to an mixed with a monomer mixture having a specific composition and, thereafter, an anionic or nonionic water soluble polymer manufactured by the same polymerization method is added to the resulting mixture to achieve the treatment of used paper manufacturing wastewater.
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