Anaerobic digestion of excess sludge is the key node to achieve “carbon neural” in wastewater treatment plants. Conventional anaerobic digestion technology is limited by insufficient hydrolysis and low methanogenesis. Therefore

both quantity and quality of the produced methane cannot meet the standard for the practical engineering application because of low biochemical methanogenesis potential (B0) of waste activated sludge and methanogenesis rate (k). Nanozero valent iron (NZVI) has been considered to have a great application potential in enhancing sludge anaerobic digestion since NZVI addition can lower oxidation reduction potential (ORP)

and thus create a more favorable condition for methanogens; NZVI also served as an electron donor to improve methane product rate. In this study

effects of different dosages of NZVI (0

100

300

600

1000 mg·L-1) on methane production in anaerobic digestion was evaluated based on B0 and k via first order kinetics. The results demonstrated that NZVI can improve methane production mainly through enhancing refractory organics degradation to improve B0 rather than methanogensis rate (k).