Flocculation is a way of controlling clay turbidity by adding substances to water that facilitate the formation of bridges between particles (Fig. 2), allowing them to combine into groups of small particles called “flocs” (Fig. 3). Metal salts make good flocculants, depending on pH. These hydrolyzed metal compounds destabilize colloids by shrinking the layer of positively charged ions surrounding clay particles, which increases the attraction of
one particle to another (coagulation). Hydrolyzed metals also can be adsorbed onto the surfaces of clay particles and create bridges to other particles (flocculation). As these particles begin to settle, they ensnare other particles, become progressively heavier, and settle
much more readily from suspension.