Abstract: A process and apparatus for removal of ash from a waste activated sludge stream includes a pressure regulator for controlling the pressure of incoming waste activated sludge containing water or supernatant, carbon and ash as suspended solids; a first stage separation including a plurality of parallel mounted hydrocyclones for receiving the controlled pressure incoming waste activated sludge for separation into a first fluid output containing substantially supernatant and carbon and a second fluid output containing a greater concentration of ash; and a second separation stage including a vibrating screen which receives the second fluid output from the first separation stage, such vibrating screen allowing substantially only the passage of supernatant and carbon therethrough thus producing a third fluid output and a fourth output of ash concentrate which can be ultimately removed from the process.