Two phase anaerobic codigestion of organic waste and activated sludge: bench study and implementation potential in energy and material (VFA) recovery.

The following study dealt with the application of the anaerobic co-digestion process for production of biohythane and volatile fatty acids (VFA). The aim of the paper is to investigate performances in a two-phase thermophilic anaerobic co-digestion process applied on waste activated sludge and biowaste. Hydrogen and methane production reached values of 29 l/kgTVS and 287 l CH4/kgTVS respectively when operating with a total hydraulic retention time of 19d (3d in the first phase and 16d in the second phase) and organic loading rates of 16 and 3 kg TVS/m3d, respectively. At the same time, RBCOD production was also investigated in order to consider an integrated approach on waste and wastewater cycles. Specific VFA production of 426 gVFA/kgTVSBIOWASTE was obtained from the first phase of the process. An overall assessment coming from the implementation of the approach on a 70.000 AE basin was also presented, based on pilot scale results obtained.