FLOCCULANT TREATMENT METHOD

PROBLEM TO BE SOLVED: To reduce a remaining polymer flocculant in solid-liquid separation treatment water by a simple means, in an flocculation treatment method for separating a solid and a liquid after adding an inorganic flocculant and a polymer flocculant thereto.SOLUTION: In the flocculation treatment method having a first adding process for adding the inorganic flocculant to raw water, a second adding process for adding the polymer flocculant to the raw water succeeding to the first adding process, and a solid-liquid separation process for separating a solid and a liquid succeeding to the second adding process, the polymer flocculant is further added to the raw water in the first adding process, and the total amount of an addition quantity of the polymer flocculant in the first adding process and an addition quantity of the polymer flocculant in the second adding process is set to be a target addition quantity which is set in advance. In the first adding process, the polymer flocculant at 25 to 35% of the target addition quantity is added, and in the second adding process, the polymer flocculant at 75 to 65% of the target addition quantity is added.