 Due to the presence of the powdered activated carbon, the sludge settles, thickens, and dewaters better compared to conventional activated sludge processes.These solids can be wasted and disposed of as a slurry, dewatered to a compact, stable cake, or pumped as a slurry to a wet air oxidation unit for further processing to regenerate the carbon and destroy the biological solids.The system as it exists today was developed in the 1970s under a collaborative effort between DuPont and Zimpro.