Question

Which of the following is present in activated sludge?

• A. Bacteria
• B. Yeast
• C. Protozoa
• D. All of the above

Answer 1

The correct option is D All of the above

The activated sludge consists of the microbes that are capable of breaking down the organic mass present in the sewage. It contains bacteria, yeast and protozoa. After each process of aerobic degradation, the activated sludge is reused for the next batch of degradation. In activated sludge systems the new cells formed in the reaction are removed from the liquid stream in the form of a flocculent sludge in settling tanks. A part of this settled biomass, described as activated sludge is returned to the aeration tank and the remaining forms waste or excess sludge.

Hence, the correct answer is 'All of the above'.