Enhancing the performance and stability of the anaerobic digestion of sewage sludge by zero valent iron nanoparticles dosage

This work studied the effects on the anaerobic digestion of sewage sludge by zero valent iron nanoparticles (NZVI) dosage. Biochemical methane potential tests were carried out with 5-9 mg/g_VS (99.7%, 40-60 nm). The biogas yield increased from 132 (control) to 310 mL/g_VS with 9 mg/g_VS. The methane content increased from 63.2% (control) to 77.6% with NZVI, which corresponded to a maximum yield of 238 mLCH₄/g_VS with 9 mg/g_VS. The maximum VS reduction was 19.6%. The highest INT-ETS activity (20.1-37.1 µgINT_red/g_VS·h) corresponding to the maximum values of sCOD was reached within the first days. NZVI decreased the ORP to -300 mV and increased the VFA's concentration (+2000 mg/L). The ORP-VFA-pH analysis showed that NZVI promoted the acidogenesis-acetogenesis without acidification. That is, NZVI was effective in intensifying the performance and stability of the process.