High Solids Anaerobic Digestion Process to Treat High Strength Municipal and Industrial Organic Waste

The high solid anaerobic digestion (HiSAD) system is a combination of a first stage plug-flow solid digester and second stage attached growth anaerobic filter packed with porous media. Organic wastes of 20% or more solids content can be digested with this process operating at mesophilic/thermophilic condition while liquid digestate is recirculated continuously between the anaerobic filter and the solid digester. This novel technology was initially developed and tested by a local US university. During the study, this technology showed great potential to achieving ≥70% volatile solids reduction (VSR) without any mixing in both stages. Final products include methane-laden biogas, low volume of high quality Biosolids, and a nutrient rich liquid effluent.A pilot-scale HiSAD unit configured with 1450-gallon solid digester (SD) and 850-gallon anaerobic filter, filled with lava rock, has been established for solid waste management at poultry (chicken) processing plant in Richmond, VA. The solid digester was fed with 130±10 gallons/day solids characterized by 18.5% TS of which >97% volatile solids. Preliminary findings indicate that the high solids digester pilot unit attained a methane yield of 49 m3/tones VS and volatile solids reduction rates of 53%. To optimize the process, mobile bench HiSAD simulator was built using much smaller vessels and apparatuses. It is expected to help optimize the process to achieve a methane yield of >100 m3/tonnes VS and volatile solids reduction rate of >70% without changing operational parameters of large HiSAD pilot unit.