The feasibility study of the application of the AGS process for treating high-strength liquid anaerobic digestate

This study aimed to evaluate organic matter and nitrogen removal by the aerobic granular sludge (AGS) process for high-strength liquid anaerobic digestate from an actual resource recovery facility. Specifically, the effect of different hydraulic retention time (HRT) on organic matter and nitrogen removal was investigated. The results revealed that the system operated with a HRT of 10.5 days, achieving an organic loading rate (OLR) of 0.54 kg-COD/m3/d and an organic matter removal rate of 64%. The organic matter removal efficiency of the AGS improved as the OLR increased. Finally, the organic matter removal efficiency achieved 73% at an OLR rate of 0.94 kg-COD/m3/d. However, the nitrification efficiency was maintained at 99.9% even though the nitrogen loading rate was increased. In the ozone reactor, organic matter removal efficiencies were relatively low due to the presence of refractory organic matter. The specific nitrification rate (SNR) value was calculated to be 0.121 kg NH4⁺-N/kg MLVSS/day, while the specific denitrification rate (SDNR) value measured 0.228 kg NO3⁻-N/kg MLVSS/day. This study demonstrates the applicability of the AGS process for the treatment of high-strength liquid anaerobic digestate and provides basic operating parameters for process design.