Chloramine produces which characteristic and is generally relatively what for Giardia compared to chlorine?

• A. short-lasting residual, ineffective, inactivating most cyst-forming bacteria
• B. lower concentrations of THMs, ineffective, inactivating Giardia
• C. higher concentrations of DBPs, ineffective, inactivating most cyst-forming bacteria
• D. Long-lasting residual, effective Giardia

Answer: (B)

Chloramine is a disinfectant that gives a longer-lasting residual in the distribution system but is less potent for rapidly inactivating certain pathogens, like Giardia cysts. It forms far fewer disinfection byproducts, especially trihalomethanes (THMs), than free chlorine. Giardia cysts are more resistant to chloramines, so chloramine treatment generally inactivates Giardia less effectively than chlorine does. This combination—lower THM formation and weaker Giardia inactivation—matches the statement that chloramine yields lower THMs and is relatively ineffective against Giardia compared with chlorine.