ANS:C - ribbed

The plate in a plate and frame filter press typically has a curved surface.

Plate and Frame Filter Press:

1. Structure:
   • A plate and frame filter press consists of a series of vertical plates and frames arranged alternately.
   • Each frame holds a filter medium (cloth or paper) and forms a chamber for solids collection.
   • Plates are typically made of metal or plastic and have a textured or curved surface to support the filter medium and facilitate slurry flow.
2. Introduction of Slurry:
   • Slurry (the mixture of solids and liquid to be filtered) is introduced into each frame of the filter press through a port on the plate.
   • The slurry then passes through the filter medium, with solids retained as a cake on the medium and liquid (filtrate) collected through drainage ports.
3. Plate Surface:
   • The plate in each frame of a plate and frame filter press usually has a curved surface. This curved surface helps in maintaining uniform pressure distribution across the filter medium and ensures efficient filtration.
   • The curved shape of the plate also helps in directing the flow of slurry and facilitating the discharge of filtrate.

Conclusion: