CONFLICT OF INTEREST The authors declare that they have no known personal financial interests or relationships that influenced the work reported in this paper. DATA AVAILABILITY STATEMENT Data are available upon request from the corresponding author. REFERENCES 1 and , Trending topics and open questions in anaerobic ammonium oxidation. Curr Opin Chem Biol 49: 45–52 (2019). 2, , , , , et al., Anammox-mediated municipal solid waste leachate treatment: a critical review.