Optimizing temperature and feedstock interactions for efficient vermibioconversion of pulp and paper mill sludge...

The efficiency of oil contaminated pulp and paper mill sludge (PPMS) stabilization by Eisenia fetida strongly depends on optimal temperature conditions for nutrient recovery and organic pollutant reduction. In Western Newfoundland, Canada, fluctuations in environmental temperature (< 0 °C to 20 °C), limit the year-round viability of vermicomposting. Therefore, PPMS (TS) and PPMS amended cow manure (TSC) were vermicomposted over a 70-day period at three controlled temperatures (12 °C, 17 °C, and 22 °C) to assess the effects of thermal conditions on PPMS stabilization, and vermiremediation efficiency, and population dynamics of E. fetida. While pH remained stable at 17 °C and 22 °C, it decreased significantly at 12 °C (p < 0.000), whereas electrical conductivity increased significantly across all treatments (p < 0.000). The biodegradability coefficient was significantly higher (p < 0.008) in TS at 17 °C and 22 °C while maximum carbon (C) loss and nitrogen (N) enrichment occurred in TSC at 22 °C, resulting in a reduced C:N (<20) by day 56. Oil degradation was faster in TSC compared to TS at 17 °C and 22 °C. A significant increase in macronutrients (P, Na, K, Ca, Mg) and micronutrients (B, Mn, Fe, Al) were observed at 17 °C and 22 °C with the highest enrichment in TSC, followed by TS (p < 0.001). A slight increase in potentially toxic elements (As, Co) was detected in TSC, whereas Zn and V were more prominent in TS at 12 °C. TS exhibited higher levels of Cd, Cu, Ni, and Cr, while Pb and Mo were elevated in TSC at 22 °C. However, all remained below Canadian Council of Ministers of the Environment (CCME) guideline limits. Growth and reproduction of E. fetida and vermicompost production were significantly enhanced (p < 0.0001) at 17 °C and 22 °C, peaking on day 42 while lower at 12 °C. Overall, temperature between 17 °C and 22 °C optimized PPMS vermicomposting and are feasible from late spring to mid fall in Corner Brook, Newfoundland and Labrador, Canada.