Analysis of mesophilic and thermophilic anaerobic digestion process applied to pressed biowaste during transient/stressed conditions and co-digestion with waste activated sludge

The anaerobic digestion and co-digestion with waste activated sludge of liquid pressed biowaste from kerbside collection was studied. The research focused on the aspects related to a comparison between mesophilic and thermophilic conditions, also considering the processes stability during "non-steady-state" conditions in specific perturbation in loading rate. The second part of the research was specifically dedicated to the study of the co-digestion with WAS. The effect on biogas yield and stability parameters of transient testing is investigated. Continuous operation results indicated that biowaste juice AD was viable at all operating conditions tested, with the greatest specific gas production of 0.94 m3/kgTVSfed at an organic load rate of 4.7 kgTVS/m3d in thermophilic conditions. The contents of heavy metals and pathogens of fed substrate and effluent digestates were analyzed. These showed low levels for both the parameters thus indicating the good quality of digestate and its possible use for agronomic purposes.