Describe the role of Microbes in sewage treatment plant.

Explanation

Primary Treatment: This step involves physical removal of floating and suspended solids from sewage through filtration and sedimation. Initially, floating debris is removed through sequential filetration. The filtrate is kept in large open setting tanks where grit (sand, silt and small pebbles) are removed by sedimentation. sometimes, alum or iron sulphate is added for flocculation and setting down of solids. the sediment is called primary sludge, while the supernatant is called effluent. the primary sludge is subjected to composting or land fill. the effluent from the primary settling tank is taken for secondary treatment.