Question

Explain the different steps involved during primary treatment phase of sewage. [2]

Answer 1

The primary phase of sewage treatment involves physical removal of particles through filtration and sedimentation. Initially, floating debris is removed by sequential filtration[0.5]
Then the grit is removed by sedimentation.[0.5]
All solids that settle form the primary sludge,[0.5] and the supernatant forms the effluent [0.5] The effluent from the primary settling tank is taken for secondary treatment.