Alleviating the nitrite stress on anaerobic ammonium oxidation by pyrolytic biochar

The nitrite (NO2-) inhibition in anaerobic ammoniumoxidation (anammox) process iswidely reported. Here, the effects of three pyrolytic biochars (CS300, CS550 and CS800) were investigated to alleviate NO2- stress on anammox process under exposure of varied NO2--N concentrations (70, 200, 400 and 600mg L-1). No nitrite inhibition was observed at 70 mg N L-1. However, the total nitrogen removal efficiency (TNREs) decreased with NO2--N concentration increased, while the biochar-amended groups achieved higher TNREs than the control (CK). At 200 mg N L-1, the TNREs were 60.2%, 99.0%, 98.5% and 86.6% for CK, CS300, CS550 and CS800, respectively. At 400 mg N L-1, the TNREs were 23.3%, 56.0%, 37.1% and 29.7% for CK, CS300, CS550 and CS800, respectively. At 600mg N L-1 in which severe inhibitionwas observed, the TNREswere increased by 231% (p= 0.002), 149% (p= 0.014), and 51.0% (p= 0.166) for CS300, CS550 and CS800, respectively, as compared to CK, with the corresponding specific anammox activity increased by 3.1-, 2,0- and 1.1-folds, respectively. CS300 enriched the relative abundance of Candidatus Kuenenia and increased the gene copies of functional genes (hzsA, hdh, nirS and nirK). Besides, CS300 effectively alleviated the suppression of three membrane-associated enzyme complexes for anammox electron transport chain, indicating the possible contribution of redox-active moieties of CS300 to energy conversion metabolism for mitigating the NO2--N inhibition. This study provided an effective strategy for alleviating NO2--N stress by applying an environmentally compatible material (biochar) on anammox process. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study demonstrates that the use of pyrolytic biochars can alleviate nitrite inhibition in the anaerobic ammonium oxidation (anammox) process, leading to an increased total nitrogen removal efficiency.