High-rate stabilization and associated air emissions prospected during on-site in-vessel sewage sludge composting

On-site in-vessel composting of sewage sludge is considered to be applied in Israel for peripheral wastewater treatment plants (WWTPs). Based on lab-scale simulations using municipal sewage sludge and green waste, this study identifies a prospective range of values related to biomass stabilization during short-term processing. Within two weeks, 26–30% of the initial organic carbon was released as CO₂, potential heat formation was decreased by 73–82%, and odor emissions by 87–99.5%. This reduction was mainly associated with co-decrease of NH₃, dimethyl disulfide, and dimethyl trisulfide. Phytotoxicity was reduced by 28–52% whereas some residual toxicity might be attributed to non-biodegradable inorganic compounds. Stabilization rates observed in flexibly controlled lab-scale simulations can represent closed and efficiently aerated large-scale industrial systems. These prospective ranges of stabilization parameters are critical for deciding on the necessity of a curing stage for on-site enclosed installations in WWTPs.