How does primary sludge differ from activated sludge? What type of changes in the sludge is carried out in an anaerobic sludge digester? Give the composition of biogas produced in the sewage treatment plant.
Primary sludge is made up of all solids, such as soil and small stones, that settle in the settling tank during sewage treatment. The sediment of bacterial flocs in the settling tank following biological treatment is known as activated sludge. Slime and fungal filaments bind bacteria together to form flocs. A portion of the activated sludge is used as inoculum in the aeration tank, and the rest is sent to the anaerobic sludge digester, which is a big tank. Other bacteria that grow anaerobically in this tank consume the bacteria, fungus, and cellulose in the sludge. Biogas is a mixture of methane, hydrogen, and carbon dioxide created in sewage treatment plants.
