Vermistabilization of paper mill wastewater sludge using Eisenia fetida

Vermistabilization of paper mill wastewater sludge (PMS) spiked with cow dung (CD) at ratios of 0%, 25%, 50%, 75%, and 100% was carried out employing the earthworm, Eisenia fetida. A total of five treatments were established and changes in chemical and microbial properties of mixtures were observed. Vermistabilization caused decreases in total organic carbon, C:N ratio and cellulose by 1.2–1.5, 4.6–14.6, and 2.3–9.7-fold, respectively, but increases in pH, electrical conductivity, ash content, totN, availP, totP, exchK, Ca, Na, and N – NO 3 - of 1.06–1.11, 1.2–1.6, 1.3–1.6, 3.8–11.5, 4.1–6.5, 5.7–10.3, 1.7–2.0, 1.16–1.24, 1.23–1.45, 4.2–13.4-folds, respectively. PMS with 25–50% of CD showed the maximum mineralization rate. The fungal, bacterial and actinomycetes population increased 2.5–3.71, 3.13–8.96, and 5.71–9.48-fold, respectively after vermistabilization. The high level of plant-available nutrients indicates the suitability of vermistabilized material for agronomic uses.