Understanding the Vermicompost Process in Sewage Sludge: A Humic Fraction Study

The objective of this research was the characterization of the humic substances isolated from domestic sewage sludge (DSS) in natura and after three months of vermicomposting, treated with Eisenia foetida, in order to help the understanding about the main differences between the maturation degree of both organic residues. Elemental analysis, infrared and UV-Vis spectroscopy were used for the characterization of the humic substances. By comparing both humic substances, those from DSS in natura presents a great potential as fertilizer, whereas the humic substances from DSS vermicompost produced in three months shown a satisfactory percentage of humic acids, thus being able to be incorporated into the soil as a conditioner or fertilizer and thereby offering an adequate environmental destiny for this residue, transforming an unwanted material into a valuable product. It is notable to mention that the number of viable helminth ova is reduced during the process of vermicomposting. It has shown that vermicomposting process is a powerful tool to increase the stability of this residue.