Quality of Vermicompost and Microbial Community Diversity Affected by the Contrasting Temperature during Vermicomposting of Dewatered Sludge

This study aimed to investigate the effects of temperature on the quality of vermicompost and microbial profiles of dewatered sludge during vermicomposting. To do this, fresh sludge was separately vermicomposted with the earthworm Eisenia fetida under different temperature regimes, specifically, 15 °C, 20 °C, and 25 °C. The results showed that the growth rate of earthworms increased with temperature. Moreover, the lowest organic matter content along with the highest electrical conductivity, ammonia, and nitrate content in sludge were recorded for 25 °C indicating that increasing temperature significantly accelerated decomposition, mineralization, and nitrification. In addition, higher temperature significantly enhanced microbial activity in the first 30 days of vermicomposting, also exhibiting the fastest stabilization at 25 °C. High throughput sequencing results further revealed that the alpha diversity of the bacterial community was enhanced with increasing temperature resulting in distinct bacterial genera in each vermicompost. This study suggests that quality of vermicompost and dominant bacterial community are strongly influenced by the contrasting temperature during vermicomposting of sludge, with the optimal performance at 25 °C.