Which polymer would most likely be used to coagulate turbidity?

• A. Anionic
• B. Nonionic
• C. Cationic
• D. Amphoteric

Answer: (C)

Coagulation and flocculation rely on charge interactions between particles and the polymer. Turbid water typically has negatively charged colloids on their surfaces, so a positively charged polymer is attracted to and adsorbs onto these particles. This neutralizes the surface charge and, as the polymer chains bridge between multiple particles, promotes formation of larger flocs that can settle or be filtered out. That makes a cationic polymer the most effective for turbidity removal. Anionic polymers would repel the negatively charged particles, nonionic polymers lack the charge needed to initiate neutralization, and amphoteric polymers’ behavior depends on pH, making their performance less predictable.