Which term best describes chemicals used to prevent metal ions from interfering with water quality by binding them?

• A. Chelating agents
• B. Buffering agents
• C. Sequestering agents
• D. Coagulants

Answer: (C)

Metal ions in water can cause problems like scale formation, discoloration, and interference with disinfection. Sequestering agents bind those metal ions, forming stable soluble complexes that keep the metals from reacting, precipitating, or interfering with treatment steps. This keeps the metals in solution and reduces their impact on water quality and system performance. Chelating agents are a subset that binds metals with multiple bonds to form a ring structure, which is a specific way of sequestering, but the broader term used in water treatment is sequestering agents. Buffering agents control pH, and coagulants help particles come together for removal, which are separate roles.