Vermi-sanitization of toxic silk industry waste employing Eisenia fetida and Eudrilus eugeniae: Substrate compatibility, nutrient enrichment and metal accumulation dynamics

Detoxification of silk processing effluents and sludge (SPES) through composting approaches is a new idea. This study examined the biodegradation potential of two epigeic earthworms (Eisenia fetida and Eudrilus eugeniae) in different SPES and cow dung (CD) mixtures in comparison with composting. N, P, S, Fe and Mn availability significantly increased upon vermicomposting compared to aerobic composting. The alkaline pH of the feedstocks satisfactorily neutralized under vermicomposting. The Ca-K availability and cation exchange dynamics readily stabilized due to vermicomposting. Interestingly, Eisenia fetida exhibited greater adaptability towards the toxic SPES materials than Eudrilus eugeniae, which was accompanied by 60-70% reduction of Cd, Cr, Zn and Pb levels in Eisenia system, whereas metal accumulation ability of Eudrilus eugeniae was remarkable. Moreover, both the species equally contributed in augmentation of beneficial (N-fixing and P-solubilizing) microorganisms in the feedstocks. Overall, nutrient enrichment and sanitizing potency of vermitechnology was explicitly manifested in SPES + CD (1:1) combination.