Degradation and characteristic changes of organic matter in sewage sludge using Vermi-biofilter system

•Vermi-biofilter (VF) was an efficient sludge treatment, especially earthworm-treated.•60 days VF system reached an O demand, soluble C reduce and earthworm density increase in sludge EBOM.•Organic matters were identified to be increased by 10 days earthworm-treated and then degradation.

Vermi-biofilter (VF) System could be an efficient sludge treatment unit in regard of rates and extents of total chemical oxygen demand (TCOD) removal, particularly the first 10 days earthworm-treated. This study characterized the organic matter in sludge before and after VF system treatment, with or without earthworm stage. The 60 days earthworm-treated VF system reached a TCOD removal of 10,450 mg/L, bulk DOC removal of 89.5 mg/L, and earthworm density increase from 32 g/L to 43 g/L in sludge EBOM in 60 days of VF system operation. The aromatic proteins, soluble microbial byproduct-like fluorescent compounds and carboxylic components, aliphatic components (C-H related), hydrocarbon and carbohydrate materials were identified to be principally increased by 10 days earthworm-treated and then degradation in the nest days under VF system.