Thickened WAS is mixed with a small dose of  caustic soda (1.75 l/m3).
 Sludge is heated in a loop through a high-efficiency heat exchanger.
 Sludge is fed into PONDUS and goes through hydrolysis. The sludge is heated with 140 °F to 160 °F water from a Combined Heat and Power (CHP) unit or boiler. Retention time may differ in reactor zones due to varying sludge properties. The reactor operates under atmospheric pressure and is connected to the atmosphere or bio-filter. After the hydrolysis process, sludge leaves the reactor close to a neutral pH level and the remaining thermal energy can be used in the anaerobic digester .
 Thickened primary sludge and hydrolyzed sludge is mixed to achieve an ideal mesophilic temperature of the combined sludge and then pumped into the digester . If needed, additional heat can be brought into the digester through a  heat exchanger.