ABSTRACT
Hydrothermal liquefaction (HTL) is a promising method for municipal sludge valorization through waste minimization and biofuel production. The process wastewater, HTL aqueous, presents a significant challenge for scale-up due to recalcitrant compounds. In this study, granular activated carbon (GAC) was used to remove potential inhibitors from HTL aqueous through adsorption to enhance aerobic and anaerobic biological treatment. GAC removed up to 61â¯% chemical oxygen demand (COD), 50â¯% biochemical oxygen demand (BOD) and potential inhibitors, such as total phenolic compounds (87â¯%) and N-heterocycles (90â¯% of pyridines) at 100â¯g/L. Conversely, most volatile fatty acids remained in HTL aqueous. Subsequently, mesophilic and thermophilic specific methane potential increased by up to 97â¯% and 83â¯%, respectively. BOD increased by up to 50â¯%, which enhanced BOD/COD ratio from 81â¯% to 93â¯% before and after adsorption. This study established the groundwork for HTL aqueous adsorption, described mechanism for pollutant removal, and provided insights for biological treatment.
