Aquatic Pollution and Coastal Management

Unit 2 : Sewage and domestic wastes, treatment and reuse

2.5.1.Preliminary Treatment
The major aim of preliminary treatment is to remove the larger solid debris and floating materials (wood, paper rags and plastics).

The waste is passed through screens consisting typically of parallel iron bars for the removal of floating objects (rags, plastics and wood). ‘comminutor’ or macerator is often provided for grinding the coarse material into smaller particles. A separate grit chamber is often provided where the waste is given retention for only a few minutes to settle down grit and other heavy materials.