1
Question
Match column A with column B and choose the correct option.
Column A
Column B
I. Primary sludge
A. Production of biogas
II. Activated sludge
B. Solids like grit
III. Anaerobic sludge digesters
C. Contains aerobic heterotrophic bacteria
Match column A with column B and choose the correct option.
| Column A | Column B |
| I. Primary sludge | A. Production of biogas |
| II. Activated sludge | B. Solids like grit |
| III. Anaerobic sludge digesters | C. Contains aerobic heterotrophic bacteria |
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Solution
The correct option is A I - B, II - C, III - A
Sewage, also called municipal waste water, contains human excreta, organic wastes and various pathogens (disease causing microorganisms). Releasing it directly into the water bodies poses a high threat to aquatic life and causes water pollution. Hence, the sewage is treated in the sewage treatment plants (STPs) before it is released into the water bodies.
Primary treatment of sewage includes removal of particles from the sewage by filtration (to remove the floating debris) and sedimentation (to remove the heavier particles). The solids that settle form the primary sludge. It usually consists of soil and small pebbles which are called grit.
After sedimentation, the fluid that remains above the sediment is called as effluent and it is subjected to secondary treatment. Secondary treatment involves oxidation of the organic matter present in the sewage by the enzymatic actions of aerobic microbes, in the presence of oxygen.
In this process the effluent is passed into huge aeration tanks where it is continuously agitated by stirring and pumping it with air. This leads to the rapid growth of heterotrophic aerobic microbes into flocs (mesh like structures consisting of masses of bacteria and filamentous fungi). These flocs digest the organic wastes present in the sewage and degrade it.
Once all the organic matter in the sewage is degraded, the sewage is allowed to sit undisturbed in the settling tanks. This causes the microbial flocs to settle down as sediment and it is referred to as activated sludge.
Most of the activated sludge is pumped into large tanks known as anaerobic sludge digesters in which anaerobic microbes digest the organisms present in the activated sludge and produce biogas (mixture of gases like methane, hydrogen sulphide and carbon dioxide).
Hence, option a is correct.
Sewage, also called municipal waste water, contains human excreta, organic wastes and various pathogens (disease causing microorganisms). Releasing it directly into the water bodies poses a high threat to aquatic life and causes water pollution. Hence, the sewage is treated in the sewage treatment plants (STPs) before it is released into the water bodies.
Primary treatment of sewage includes removal of particles from the sewage by filtration (to remove the floating debris) and sedimentation (to remove the heavier particles). The solids that settle form the primary sludge. It usually consists of soil and small pebbles which are called grit.
After sedimentation, the fluid that remains above the sediment is called as effluent and it is subjected to secondary treatment. Secondary treatment involves oxidation of the organic matter present in the sewage by the enzymatic actions of aerobic microbes, in the presence of oxygen.
In this process the effluent is passed into huge aeration tanks where it is continuously agitated by stirring and pumping it with air. This leads to the rapid growth of heterotrophic aerobic microbes into flocs (mesh like structures consisting of masses of bacteria and filamentous fungi). These flocs digest the organic wastes present in the sewage and degrade it.
Once all the organic matter in the sewage is degraded, the sewage is allowed to sit undisturbed in the settling tanks. This causes the microbial flocs to settle down as sediment and it is referred to as activated sludge.
Most of the activated sludge is pumped into large tanks known as anaerobic sludge digesters in which anaerobic microbes digest the organisms present in the activated sludge and produce biogas (mixture of gases like methane, hydrogen sulphide and carbon dioxide).
Hence, option a is correct.
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