Treatment of excess sludge coming from biological purification process includes digestion step and wet oxidation step

摘要

Treatment of excess sludge coming from a biological purification process includes a digestion step and a wet oxidation step. The oxidation takes place at 50 - 180 deg C and 2 - 40 bar. An Independent claim is included for a plant for performing the treatment. The plant has digester(s) and device(s) for performing the wet oxidation. Preferred Features: The sludge is treated so that its pH is 2 - 11 before it is wet oxidized for 10 - 180 minutes. It is then digested and the remaining sludge returned for more oxidation. The oxidation step uses air, oxygen-enriched air and/or hydrogen peroxide in the presence of a heterogeneous or homogeneous catalyst. Some of the gas present during oxidation is recirculated after it has passed over the catalyst to ensure it has sufficient contact time with the sludge. The digestion may be mesophilic aerobic or thermophilic anaerobic and has an immobilized biomass. The digester has an emptying rate /- 70% and a specific surface /- 90 m<2>/m<3>.