What does 'Break-point Chlorination' signify in water treatment?
- AThe point where chlorine is first added to the water
- BThe point where the chlorine demand is at its maximum
- CThe point beyond which any further addition of chlorine appears as Free Residual ChlorineCorrect
- DThe point where only combined residual chlorine exists
Solution
Concept
Break-point chlorination mechanics
Formula
Total Chlorine Residual = Free Residual + Combined Residual
Step-by-step solution
1. Adding chlorine to water initially oxidizes inorganic compounds and forms combined chloramines. 2. Continued chlorine addition oxidizes chloramines until reaching a minimum residual known as the break point. 3. Beyond the break point, all chlorine demand is satisfied, and any added chlorine remains as free residual chlorine. 4. Hence, option C correctly defines break-point chlorination. Answer: C
Explanation
Break-point chlorination represents the stage in water disinfection where all reducing agents and ammonia/organic compounds (forming chloramines) have been completely oxidized. Beyond this critical inflection point, any supplementary chlorine added to the water ceases to react and appears directly as free available residual chlorine.
Why the other options are wrong
A) Initial chlorine addition marks the start of dosage, not the break-point. B) Chlorine demand is completely satisfied at the break-point rather than at maximum demand. D) Combined chloramines dominate prior to the break-point, whereas free residuals dominate beyond it.
Shortcut
Break-point = Point where all added chlorine appears as FREE residual.
Common mistake
Confusing break-point with the peak of combined chloramine formation.
Correct answer: C) The point beyond which any further addition of chlorine appears as Free Residual Chlorine