Adding activated carbon to the system with added zero-valent iron further improves anaerobic digestion performance by alleviating ammonia inhibition and promoting DIET

Abstract

The addition of activated carbon (AC) may improve the efficiency of anaerobic digestion (AD) system to which zero-valent iron (ZVI) has been added. This study investigated the effects of the addition of AC on the AD system with ZVI added. Results showed that the cumulative methane production of 5 g/L ZVI + 5 g/L AC (5ZVI + 5AC) was 2.77–35.0% higher than that of 5 g/L ZVI, 10 g/L ZVI and control. The combined addition shortened the time to reach maximum daily methane yield by 18.2% compared to ZVI groups. Meanwhile, 5ZVI+5AC had the lowest free ammonia concentration (average 461 mg/L) amongst all groups, thus effectively alleviating the ammonia inhibition. Microbial community analysis showed that the combined addition of ZVI and AC enriched hydrogenotrophic methanogens (Methanoculleus) and direct interspecies electron transfer related microorganisms (Syntrophomonas and Methanosaeta), possibly enhancing electron exchange to accelerate methane production.