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/gVS (99.7%, 40-60 nm). The biogas yield increased from 132 (control) to 310 mL/gVS with 9 mg/gVS. The methane content increased from 63.2% (control) to 77.6% with NZVI, which corresponded to a maximum yield of 238 mLCH4/gVS with 9 mg/gVS. The maximum VS reduction was 19.6%. The highest INT-ETS activity (20.1-37.1 µgINTred/gVS·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.

Nanoferrosonication: A novel strategy for intensifying the methanogenic process in sewage sludge.

In this work, the effect of coupling ultrasonic pretreatment with dosing of zero-valent iron nanoparticles (nanoferrosonication, "NFS") to improve the anaerobic digestion of sewage sludge was studied. Biochemical methane potential tests were conducted at 15,000 and 25,000 kJ/kgTS and their combinations with 2 and 7 mgFe0/gVS. The biogas yield increased from 106 (control) to 143 (25,000 kJ/kgTS) and 308 mL/gVS with NFS (7 mgFe0/gVS + 15,000 kJ/kgTS). The methane content increased from 55.6 to 66%, and the maximum VS removal was 11.5% at 7 mgFe0/gVS + 15,000 kJ/kgTS. The results demonstrated that NFS was effective in intensifying the process.