Patent ID: 7745529

Claim:
A flocculant composition comprising a vinyl crosslinking water-soluble ionic polymer (A) having a charge inclusion ratio of 20% or more and a vinyl linear water-soluble ionic polymer (B) having a charge inclusion ratio of 5% or more and less than 20%, wherein a compounding ratio (a/b) of the vinyl crosslinking water-soluble ionic polymer (A) to the vinyl linear water-soluble ionic polymer (B) is changed according to an amount in percent by mass of 200-mesh particles based on a total mass of suspended particles in a sludge so as to satisfy 0.2≦a/b≦9 when 0<X≦10 percent by mass, 0.4≦a/b≦3 when 10<X≦20 percent by mass, and 0.1≦a/b≦2 when 20<X≦60 percent by mass, where X is an amount of percent by mass of the 200-mesh particles in the sludge, a is an amount in percent by mass of the vinyl crosslinking water-soluble ionic polymer (A), and b is an amount in percent by mass of the vinyl polymer type linear water-soluble ionic polymer (B).