Industrial Composting of Sewage Sludge: Study of the Bacteriome, Sanitation and Antibiotic Resistant Strains

Wastewater treatment generates a huge amount of sewage sludge, which is a source of environmental pollution. Among the possible alternatives for the management of this waste, industrial composting stands out as one of the most relevant. The objective of this study was to analyze the bacterial population linked to this process and to verify its effectiveness for the reduction, and even elimination, of microorganisms and pathogens present in these organic wastes. For this purpose, the bacteriome and the fecal contamination of samples from different sewage sludge industrial composting facilities were evaluated. In addition, strains belonging to the fecal indicators and pathogens, such as Salmonella, were isolated in each stage of the process. These were characterizedfor antibiotic resistance to macrolides, beta-lactams, quinolones and aminoglycosides families. Metagenomics data revealed that the process clearly evolved towards a prevalence of Firmicutes and Actinobacteria phyla, removing the fecal load. Moreover, the presence of antibiotic resistant microorganisms present in the raw materials was reduced, since these were isolated only in the bio-oxidative phase. Therefore, industrial composting of sewage sludge results in a bio-safe final product suitable for use in a variety of applications.