Environment-friendly management of textile mill wastewater sludge using epigeic earthworms: Bioaccumulation of heavy metals and metallothionein production.

In the present study, Eudrilus eugeniae and Perionyx excavatus were used for vermistabilization of textile mill sludge in different combinations with cowdung for 60 days. A higher percentage of metal removal was observed in earthworm treated mixtures for cadmium (54.5%) followed by copper (36.0%), chromium (37.0%) and zinc (35.9%). Vermistabilized textile mill sludge + cowdung (1:1) showed a maximum percentage increase in total NPK, a significant (P < 0.05) increase in bacteria, fungi, and actinomycetes with a better earthworm survival rate. A higher amount of metallothionein protein was produced by E. eugeniae than P. excavatus. Further, 100% textile mill sludge showed a number of histological abnormalities like degeneration of cells, cellular debris, and uneven cellular compartmentation while textile mill sludge with cowdung showed normal earthworm histology. Results suggest that textile mill sludge + cowdung (1:1) combination is suitable for vermistabilization of textile mill sludge.