Enhancement of Supercritical Water Oxidation for Municipal Sludge Degradation

Different measures to enhance the removal efficiency of municipal sludge by supercritical water oxidation were further studied in a batch reactor, including catalytic supercritical water oxidation, co-oxidation with methanol and multi-injection of oxidant experiments at 580 °C, 25 MPa within a total residence time of 10 min and a total oxidant coefficient of 1.1. The experimental results showed that splitting the same amount of oxidant and feeding into reactor at two different residence time had a significant enhancement on the removal of COD compared with NH₃-N, and the optimal second injection time of oxidant was 7.5 min in this investigation. Meanwhile, CuO catalyst could increase the degradation efficiency of both COD and NH₃-N, and it increased with the amount of CuO added, which was better than methanol. Moreover, combining CuO with injecting oxidant multi-stage experiment produced the maximum organics degradation efficiency of 99.9% and 83.47% for COD and NH₃-N, respectively, it demonstrates lower COD degradation of 99.58% and NH₃-N degradation of 35.69% utilizing methanol at fixed reaction condition.