Simultaneous removal of nitrate nitrogen and ammonium nitrogen by partial denitrification coupled with anammox synergy by zero-valent iron

The implications of zero-valent iron (ZVI) on performance of partial denitrification (PD) coupled with anammox process (PD-anammox) and microbial community structures were assessed in present investigation. The results indicated that removal efficiencies of nitrate nitrogen, ammonium nitrogen and total nitrogen (TN) reached 86.28 ± 0.04%, 81.05 ± 0.06% and 82.90 ± 0.80%, respectively, with 30-day addition of ZVI under ratio of ZVI to nitrate (ZVI/N), carbon to nitrate (C/N) respectively for 3 and 2.3. Moreover, the content of extracellular polymer substance elevated by ZVI, and which could substitute carbon sources, mediated electron transfer and promoted nitrogen removal efficiency. Additionally, microbiological analysis revealed that ZVI enhanced nitrogen removal process by promoting the growth of genus Ignavibacterium and Denitratisoma , which coexist with anaerobic ammonia oxidation bacterium (AnAOB) and also induced other nitrogen removal process such as heterotrophic nitrate reduction to ammonium (DNRA), nitrate-dependent anaerobic ferrous oxide (NAFO), and iron-based anammox (Feammox) process. This study offers new insights into the enhancement of the nitrogen removal process by ZVI in PD-anammox process.