Question

During sewage treatment, the microorganisms participate under which step?

• A. Primary
• B. Secondary
• C. Tertiary
• D. All of the above

Answer 1

The correct option is B Secondary

Sewage treatment is a process in which the pollutants are removed. The ultimate goal of sewage treatment is to produce an effluent that will not impact the environment. In the absence of sewage treatment, the results can be devastating as sewage can disrupt the environment.

The general processes of sewage treatment are primary, secondary and tertiary treatment. Primary treatment involves physical separation of sewage into solids and liquid by using a settling basin. The liquid sewage is then transferred to secondary treatment which focuses on removing the dissolved biological compound by the use of 'micro-organisms'. The micro-organisms usually use aerobic metabolism to degrade the biological matter in the liquid sludge. Then tertiary treatment is required to disinfect the sewage so that it can be released into the environment. The solid sewage separated from primary treatment is transferred to a tank for sludge digestion which involves anaerobic degradation using micro-organisms.

Therefore, the correct answer is option B.