Compare chlorine and chloramine as disinfectants: advantages and disadvantages.

• A. Chlorine provides strong disinfection and residual protection but forms disinfection byproducts.
• B. Chloramines form stronger disinfection with no byproducts.
• C. Chloramines form fewer byproducts and have longer-lasting residuals but can be less effective against some pathogens and require longer contact time.
• D. Chlorine and chloramine are identical in performance.

Answer: (C)

The main idea is understanding the trade-offs between chlorine and chloramine as disinfectants in water treatment: chlorine is a strong, fast-acting disinfectant that leaves a residual but tends to form more disinfection byproducts, while chloramines disinfect more slowly, form fewer byproducts and persist longer in the distribution system, but may be less effective against some pathogens and require longer contact time.

Chlorine provides rapid disinfection and leaves a protective residual that helps control microbial growth as water moves through pipes. However, it reacts with natural organic matter and other substances to form disinfection byproducts, which are a regulatory and health concern.

Chloramines form fewer disinfection byproducts because the reactions that produce DBPs are slower with ammonia present. They also last longer as a residual disinfectant, which is advantageous for maintaining safety over long distribution distances. The trade-off is that chloramines are less potent against certain pathogens and typically need a longer contact time (higher CT value) to achieve the same level of disinfection as chlorine.

That balance is why this option is the best choice: fewer byproducts and a longer-lasting residual with the caveat of potentially lower disinfection efficiency for some pathogens and the need for longer contact time. The other statements either overstate the strengths (no byproducts) or claim identical performance, which isn’t accurate.