Abstract
► Enrichment of thermophilic AD with compost and leachate reduced VFA and ammonia accumulation. ► Removal of COD and TS improved with lower VFA-to-alkalinity ratio. ► System failure was prohibited under organic shock-load with improved stability. ► Functionality was restored with 90% recovery of pre-shock CH4 generation at stable pH.
This paper examines the potential of improving the stability of thermophilic anaerobic digestion of source-sorted organic fraction of municipal solid waste (SS-OFMSW) by adding leachate and compost during inoculation. For this purpose, two stable thermophilic digesters, A (control) and B (with added leachate and compost), were subjected to a sustained substrate shock by doubling the organic loading rate for one week. Feeding was suspended then gradually resumed to reach the pre-shock loading rate (2gVS/l/d). Digester A failed, exhibiting excessive increase in acetate and a corresponding decrease in pH and methane generation, and lower COD and solids removal efficiencies. In contrast, digester B was able to restore its functionality with 90% recovery of pre-shock methane generation rate at stable pH, lower hydrogen levels, and reduced VFAs and ammonia accumulation.