Enhanced stabilization processes to produce sludge suitable for agricultural use

The requirement of a more efficient stabilization process to obtain a more stable sludge for agricultural use and better energy balance is an increasing challenge to comply with the waste hierarchy. In this prospect, the ROUTES project is addressed to assess innovative solutions with the aim to produce good quality sludge with specific concern to stabilization and hygienization. In order to increase the anaerobic stabilization performances different disintegration pre-treatments (acoustic or hydrodynamic cavitation, and thermal hydrolysis) and an aerobic post-treatment were additionally investigated as regards the effect on solubilisation, dewaterability and digestion perfomances. Pre-treated stabilization processes improved anaerobic digestion in terms of volatile solids reduction and biogas production, but digestate dewaterability worsened. Fluorescence In Situ Hybridization (FISH) quantification showed an increase of methanogens consistent with the increase of biogas produced. Aerobic post-treatment, on the contrary, had a beneficial effect on the dewaterability and the stability of the digested sludge even if with a reduction of the potential energy recovery.