Disinfection choice worldwide: The most widely used and practically ideal disinfectant for public drinking-water supplies is
Correct Answer: Chlorine
Introduction / Context:Disinfection is the final barrier in drinking-water treatment. The disinfectant should be effective, economical, and provide a measurable residual in the distribution system to guard against recontamination.
Given Data / Assumptions:
- Common municipal practice worldwide.
- Focus on primary/secondary disinfection and residual maintenance.
Concept / Approach:
Chlorine is the global workhorse disinfectant. It is effective against many pathogens, relatively inexpensive, and leaves a residual. Alternatives like ozone or UV are powerful but leave no residual; they are often paired with chlorine/chloramines downstream.
Step-by-Step Solution:
Evaluate options for microbial efficacy and residual.Identify chlorine as the agent meeting both effectiveness and residual requirements.Select chlorine as the most practical, widely used choice.Verification / Alternative check:
WHO and many national standards reference chlorine/chloramine residual targets in distribution, confirming routine reliance on chlorine-based disinfectants.
Why Other Options Are Wrong:
- Alum: a coagulant, not a disinfectant.
- Lime: used for pH/softening control, not primary disinfection.
- Nitrogen/ammonia: not disinfectants (ammonia forms chloramines with chlorine but is not used alone for disinfection).
Common Pitfalls:
- Confusing coagulants and disinfectants.
- Assuming ozone/UV are “ideal” without considering lack of residual.
Final Answer:
Chlorine.