Process for separation of ash from waste activated sludge

Process for the substantial removal of ash from a waste activated sludge stream containing supernatant, ash and carbon as suspended solids comprising the steps of:

• receiving an incoming waste activated sludge stream primarily containing supernatant, ash and carbon;
• controlling the pressure of said waste activated sludge stream and circulating said waste activated sludge at said controlled pressure to a first separation stage;
• in said first separation stage, circulating said controlled pressure waste activated sludge through a plurality of hydrocyclones in parallel flow paths to produce a first fluid output substantially containing supernatant and carbon and a second fluid output containing supernatant, carbon and a substantially greater concentration of ash than said first fluid output;
• collecting said first fluid from said hydrocyclones into a first return output for recirculation back into said sewage treatment process;
• circulating said second fluid output from said first separation stage through a second separation stage to further separate ash from said first stage second fluid output to produce a second stage third fluid output containing substantially supernatant and powdered carbon and a fourth output which is an ash concentrate for ultimate disposal.