Sludge Minimization by Thermal Lysis during Biological Wastewater Treatment - Experimental Study, Model Set Up and Calibration

Sludge minimization by thermal treatment within activated sludge process was investigated at pilot scale. A 90°C treatment was set up in the return activated sludge loop. When keeping apparent sludge age at 15 days, 90°C treatment decreased sludge production by 30.4%. However, effluent quality was altered. A sludge minimization ASM1 based model was set up and calibrated against experimental data, fractionation experiments allowed us to determine state variables for treated sludge. Biomass lysis explained sludge minimization whereas the decrease of heterotrophs growth rate yielded the higher effluent COD concentration. The calibrated model will then be used to optimize the process.