Supplementation of Wastewater Process Modelling Tools to Enable the Kinetic Analysis of Sewage Sludge Composting

This study demonstrates mathematical description of sewage sludge composting based on identifica- tion and separate characterisation of simple process parts. For a description of the microbial processes an aSM3-based mathematical model developed for autothermal thermophilic aerobic sludge digestion is used. The oxygen mass transfer was characterized in a separate way. The 2.964·10 -3 m 2 ·d -1 value of the oxygen diffusion coefficient in the sludge at 55°C indicates the strong oxygen limitation of the microbial degrada - tion. The model extended with the oxygen mass transfer description has been validated using results from composting experiments performed with different specific sludge-air surface areas and with the renewal of the sludge surface.