Performance of nitrate-dependent anaerobic ferrous oxidizing (NAFO) process: A novel prospective technology for autotrophic denitrification

• A novel NAFO system was experimentally proved viable for autotrophic denitrification.
• The nitrate volumetric removal rate was 0.073 ± 0.01 kg-N/(m3 d) by NAFO system.
• The iron content in NAFO sludge was high enough to be recycled for phosphate removal.
• NAFO system had the potential to remove nitrate and phosphorus simultaneously.

Nitrate-dependent anaerobic ferrous oxidizing (NAFO) is a valuable biological process, which utilizes ferrous iron to convert nitrate into nitrogen gas, removing nitrogen from wastewater. In this work, the performance of NAFO process was investigated as a nitrate removal technology. The results showed that NAFO system was feasible for autotrophic denitrification. The volumetric loading rate (VLR) and volumetric removal rate (VRR) under steady state were 0.159 ± 0.01 kg-N/(m3 d) and 0.073 ± 0.01 kg-N/(m3 d), respectively. In NAFO system, the effluent pH was suggested as an indicator which demonstrated a good correlation with nitrogen removal. The nitrate concentration was preferred to be less than 130 mg-N/L. Organic matters had little influence on NAFO performance. Abundant iron compounds were revealed to accumulate in NAFO sludge with peak value of 51.73% (wt), and they could be recycled for phosphorus removal, with capacity of 16.57 mg-P/g VS and removal rate of 94.77 ± 2.97%, respectively.

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