Question

Select the correct statement from following:

• A. Activated sludge in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria
• B. Biogas is produced by the activity of aerobic bacteria on animal waste (dung)
• C. Methanobacterium is an aerobic bacterium found in rumen of cattle
• D. Biogas, commonly called gobar gas, is pure methane

Answer 1

The correct option is A

Activated sludge in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria

Only 1 is correct, activated sludge contains flocs (mainly fungi and bacteria). Biogas is not pure methane gas. It contains $C{O}_2$ and other gases as well. Also, it is produced in anaerobic conditions. Methanobacterium is a methanogen and is anaerobic.