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

1. P-3, Q-4, R-2, S-1
2. P-2, Q-3, R-4, S-1
3. P-3, Q-2, R-4, S-1
4. P-1, Q-4, R-2, S-3

Correct answer: P-3, Q-4, R-2, S-1

Solution

The activated sludge process primarily involves heterotrophic bacteria (P-3) that break down organic matter. Rising of sludge is associated with denitrifiers (Q-4) that help in nitrogen removal. Conventional nitrification is carried out by autotrophic bacteria (R-2), while biological nitrogen removal involves both nitrifiers and denitrifiers (S-1) working together.

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