Feasibility Study of Vermicomposting of Textile Sludge Mixed with Cow Dung and Seed Germination Bioassay for Toxicity Evaluation of the Produced Compost

Abstract

Transformation of textile sludges into vermicomposts can convert these wastes into good quality manure. The present study investigate the feasibility of vermicomposting process to transform the textile sludge amended with cow dung in different ratio into value added products by using an epigeic earthworm Eisenia foetida. Seed germination bioassay also investigated using mustard seeds (Brassica nigra) in order to evaluate the toxicity and maturity tests of those different mixtures and their produced composts. The result revealed that the E. foetida did not survive in fresh textile sludge. But worms grew and reproduced in textile sludge spiked with cow dung feed mixtures. Presence of more than 20% of textile sludge in feed mixture affected biomass gain and cocoon production largely by earthworms. The net weight gained by E. foetida in 100% cow dung was three fold higher than the feed mixture of 50% cow dung + 50% textile sludge. After 13 weeks, maximum cocoons (56 cocoons) were counted in 100% cow dung and minimum (6 cocoons) in 50% cow dung + 50% textile sludge feed mixture. Vermicomposting resulted in pH shift toward slightly acidic, significant reduction in TOC and C:N ratio, and increase in nitrogen phosphorus and sulphur content. Total potassium content, calcium content and heavy metal’s (Cu, Cr, Pb, Zn, Fe, Mn) content were lower in the final product than initial feed material. The results of phytotoxicity test showed that all the vermicompost products had the higher seed germination percentage, root elongation percentage and germination index than their respective initial feed mixtures. The feed mixtures having the textile sludge had various phytotoxic compounds which might inhibit seed germination before vermicomposting. But the vermicomposts of different feed mixtures having the presence of 100% cow dung and 10% - 20% textile sludge were matured compost and had no phytotoxic effects as they had the germination index higher than 60. All the results indicated that vermicomposting (using E. foetida) is a suitable technology for the decomposition of textile sludge into value added materials. This textile sludge could be converted into good quality manure by vermicomposting if mixed in appropriate ratio (up to 20% on dry weight basis) with cow dung.