GATE CE 2016 Set 1 — Question 30

MCQ+1 / -0.33MediumSecondary TreatmentWastewater Treatment ProcessesEnvironmental EngineeringActivated Sludge Process

Environmental Engineering → Wastewater Treatment Processes → Activated Sludge Process

Last updated 5 September 2026

Question

Match the items in Group - I with those in Group - II and choose the right combination. Group - I Group - II P. Activated sludge process 1. Nitrifiers and denitrifiers Q. Rising of sludge 2. Autotrophic bacteria R. Conventional nitrification 3. Heterotrophic bacteria S. Biological nitrogen removal 4. Denitrifiers

Group - I	Group - II
P. Activated sludge process	1. Nitrifiers and denitrifiers
Q. Rising of sludge	2. Autotrophic bacteria
R. Conventional nitrification	3. Heterotrophic bacteria
S. Biological nitrogen removal	4. Denitrifiers

Correct answer (A) P-3, Q-4, R-2, S-1 Solution P. Activated sludge process: Primarily utilizes heterotrophic bacteria (3) to decompose organic matter. Q. Rising of sludge: This phenomenon is typically caused by denitrification (4) in the secondary clarifier, where nitrogen gas bubbles attach to sludge flocs and cause them to float. R. Conventional nitrification: This process is carried out by autotrophic bacteria (2) such as Nitrosomonas and Nitrobacter . S. Biological nitrogen removal: This comprehensive process involves both nitrifiers and denitrifiers (1) to convert ammonia to nitrogen gas. Therefore, the correct match is P-3, Q-4, R-2, S-1. Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (A) P-3, Q-4, R-2, S-1 Solution P. Activated sludge process: Primarily utilizes heterotrophic bacteria (3) to decompose organic matter. Q. Rising of sludge: This phenomenon is typically caused by denitrification (4) in the secondary clarifier, where nitrogen gas bubbles attach to sludge flocs and cause them to float. R. Conventional nitrification: This process is carried out by autotrophic bacteria (2) such as Nitrosomonas and Nitrobacter . S. Biological nitrogen removal: This comprehensive process involves both nitrifiers and denitrifiers (1) to convert ammonia to nitrogen gas. Therefore, the correct match is P-3, Q-4, R-2, S-1.

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