Which of the following is a method for sludge disposal?

Centrifugation is a method for sludge disposal because it involves using a centrifuge to separate solids from liquids through the application of centrifugal force. This process is effective in reducing the volume of sludge by concentrating the solids, enabling easier handling, transport, and further treatment or disposal.

The activated sludge process relates to the treatment of wastewater rather than its disposal. Filtration systems are primarily used for the separation of liquids from suspended solids but don't focus specifically on sludge disposal as a standalone method. Biological oxidation is a treatment process that helps to break down organic matter in wastewater; while it produces sludge, it does not directly address the disposal of that sludge. Thus, centrifugation is the most appropriate method listed for the disposal of sludge.