Direct Vermicomposting of Fresh Sewage Sludge by Using Two Epigeic Earthworm Species

Direct vermicomposting of fresh sewage sludge by two epigeic earthworm species (Eisenia foetida and Bimastus parvus) was conducted in a lab-scale experimental setup, and the performance was evaluated. The results showed that it was feasible to use both E. fetida and B. parvus to convert fresh sewage sludge without any pretreatment and blending into good quality fertilizer. Direct vermicomposting resulted in significant increase in nitrogen (35.38% - 37.48%) and phosphorus (15.35% - 18.96 %), while decrease in pH (10.22% - 20.82%), TOC (27.01% - 29.18%) and the C/N ratio (46.91% - 47.70%). Vermicomposting also caused significant reduction in concentration of heavy metal: Cu (35.17% - 37.71%), Zn (29.25% - 38.76%), Pb (21.23% - 27.40%) and Cr (16.99% - 22.96%) in sewage sludge. Study revealed that direct vermicomposting by epigeic earthworm species might be one promising disposal technique for fresh sewage sludge.