Effect of nanoscale zero-valent iron on sludge anaerobic digestion

•The experiment determined the ammonia nitrogen, pH, CODcr, VFAs, gas production and methane content , so as to explore the functional mechanism of NZVI effect on anaerobic digestion, and provide the basis of the application of nanometer materials in the sludge anaerobic digestion.•The additive amount of 1000 mg/L NZVI had the largest biogas production and mathane content.•1000 mg/L NZVI maitained the pH and ammonia nitrogen at the optimal level.•The addition of NZVI was mainly to strengthen the use of acetic acid.

Nanoscale zero-valent iron(NZVI) was prepared with a method of reduction in liquid phase by the reaction of FeSO4 and NaBH4, and characterized by SEM. This study investigated the effect of different concentration of NZVI on biogas production and methane content during the anaerobic digestion process at the medium temperature of 35 °C. The results indicated that the group with 1000 mg/L NZVI maintained ammonia at the level of 600-800 mg/L, pH between 6.5-8.0, and improved CODcr degradation rates at 2.91%; this concentration of NZVI produced maximum concentration of VFAs, which can reach 3846 mg/L, and strengthen the use of acetic acid. Relative to the control group, the system increased cumulative biogas production of 18.11%, decreased biogas production cycles of three days and increased the methane content by 6.93%.