In breakpoint chlorination, the breakpoint is reached when:
Choose the correct answer
Chlorine first appears in treated water without any reaction
All ammonia nitrogen is oxidized to N2/nitrate and free chlorine residual begins to appear
The pH reaches 7.0
Coliform bacteria are first destroyed
Correct Answer
B. All ammonia nitrogen is oxidized to N2/nitrate and free chlorine residual begins to appear
AI Detailed Explanation & IS Code Reference
Unlock the reasoning, formula path and code-linked notes inside your student dashboard.
Breakpoint chlorination: as chlorine dose increases, it reacts with organics and ammonia. Combined chlorine (chloramines) increases then decreases (oxidation to N2). Breakpoint = minimum of the curve where all NH3 is oxidized; further addition gives free chlorine residual. Typical Cl2:NH3-N ratio = 7.6:1 at breakpoint.
ScoreCardAI links this solution with subject, topic and difficulty signals so your scorecard can identify weak areas after a full mock test.
Practice more Civil Engineering questions
This MCQ belongs to AE Level Premium Test Series. Full tests include timed attempts, rank comparison and subject-wise analysis.