BEHAVIOR OF THE MESOPHILIC AND THERMOPHILIC ANAEROBIC DIGESTION IN THE STABILIZATION OF MUNICIPAL WASTEWATER SLUDGE (PART 1)

The objective of this study was to evaluate the performance of the mesophilic and thermophilic anaerobic digestion process as an alternative for the biosolids production. Biological sludge from a municipal and industrial (brewery and pulp and paper) wastewater treatment plant using a UASB reactor was used. During the operation of the mesophilic batch system., the volatile solids (VS) were reduced from 60.3% (15.67 g/L) up to 37.5% (9.67 g/L) with 31 d of treatment time. The mesophilic process presented a stable operation reducing 38% of VS with 1.76 Kg VS m(-3) d(-1) of organic load feed fulfilling with the criterion of vectors attraction reduction. However, in mesophilic conditions, the digested sludge must be post-treated with a process of pathogenic microorganism inactivation because only remove low concentrations of pathogenic microorganism. The obtained results demonstrated that the process in thermophilic conditions (55 degrees C) is capable to stabilize 3.9 Kg VS m(-3) d(-1) and to inactive the totality of fecal coliforms, Salmonella spp. and helminth ova fulfilling with the permissible limits for class A biosolids.