Change of physichochemical properties and heavy metals content in sewage sludge during its vermicomposting with Eisenia fetida

This study aimed to evaluate the vermicompost quality of sewage sludge (SS) mixed with sugar beet pulp (SBP) and cow dung (CD) wastes employing Eisenia fetida. The basic issue faced in the wastewater treatment plant is how to reduce the amount of sewage sludge? This paper discusses an in-situ vermicomposting approach for the reuse of sewage sludge. A total of 11 reactors containing various waste combinations were organized and changes in physicochemical parameters were evaluated during 90 days of the experiment. The results indicated that SS could be converted into a good quality product by vermicomposting if suitable mixing quantities are provided (50% SS, 25% SBP, 25% CD). Vermicomposting caused significant reductions in pH, TOC, the content of heavy metals, and C/N ratio, while electric conductivity and NPK content increased as compared to initial mixtures. The present study implied that the application of sewage sludge in the agricultural fields after vermicomposting could be a suitable and usable approach for sewage disposal.