NEET BIOLOGY

Detailed explanation-1: -The objective of preliminary treatment is the removal of coarse solids and other large materials often found in raw wastewater. Removal of these materials is necessary to enhance the operation and maintenance of subsequent treatment units.

Detailed explanation-2: -The surface pre-treatment are:-mechanical – grinding, brushing, polishing, blasting, tumbling, -chemical and electrochemical – alkaline degreasing, rust removal, pickling, chemical polishing.

Detailed explanation-3: -Aluminium sulphate and ferric chloride are two coagulants commonly used in water treatment. The next process is flocculation, where the water is stirred gently to enable large flocs to form. Once the large flocs have formed, the water goes to a sedimentation tank where the flocs settle out.

Detailed explanation-4: -Biofiltration. Biofiltration uses sand filters, contact filters or trickling filters to ensure that any additional sediment is removed from the wastewater.

Detailed explanation-5: -Primary treatment (also called primary sedimentation) is a sanitation technology that removes suspended solids and floating organic material (called scum) to reduce the suspended solids load for subsequent treatment processes.