Development and evaluation of an aquatic earthworm cultivation system for simultaneous waste activated sludge reduction and biomass upgrading

초록

The increasing production of waste activated sludge (WAS) necessitates low-carbon and cost-effective strategies for WAS reduction and resource recovery. This study evaluated the potential of a shallow tray system using the aquatic oligochaete Limnodrilus sp. for WAS reduction and biomass upgrading. This is the first demonstration of an aeration-free shallow tray configuration enabling low-energy aquatic worm-based WAS reduction and resource recovery. After 7 days of treatment, a maximum WAS reduction rate of 34.42 +/- 1.71% was achieved. Treatment with Limnodrilus sp. increased sludge particle size and significantly improved settleability, while the reduction in organic matter enhanced dewaterability, indicating an overall improvement in WAS properties. Meanwhile, Limnodrilus sp. biomass increased by 19.67 +/- 1.57%, with a feed conversion efficiency of 18.70%, highlighting the feasibility of converting WAS into value-added biomass. Extracellular polymeric substances (EPS) decreased markedly, indicating that EPS was a favorable WAS component for upgrading into Limnodrilus sp. biomass. In addition, populations of potential plant growth-promoting bacteria (Chryseobacterium, Exiguobacterium, etc) increased in Limnodrilus sp. feces. Compared with conventional sludge reduction technologies, the shallow tray system offers a low-energy, cost-effective, and potentially scalable strategy for WAS reduction and resource recovery, providing a promising alternative for sludge management.

키워드