[1] Thickened WAS is mixed with a small dose of [2] caustic soda (1.75 l/m3).
[3] Sludge, up to 7% total solids (TS), is heated in a loop through a high-efficiency heat exchanger. Sludge above 7% TS or high viscosity sludge can use saturated steam as a heat source.
[4] 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 differs due to varying sludge properties. The reactor operates under atmospheric pressure and connects to the atmosphere or bio-filter. After hydrolysis, sludge leaves the reactor close to a neutral pH level and the remaining thermal energy can be used in the anaerobic digester [7].
[5] Thickened primary sludge and hydrolyzed sludge is mixed to achieve an ideal mesophilic temperature of the combined sludge and then pumped into the digester [7]. If needed, additional heat can be brought into the digester through a [6] heat exchanger.
