Low temperature advanced nitrogen and sulfate removal from landfill leachate by nitrite-anammox and sulfate-anammox

Abstract Under anaerobic conditions, ammonium nitrogen (NH4+-N) can react with nitrite (NO2−-N) and sulfate (SO42-), termed nitrite-anammox (NirAnammox) and sulfate-anammox (Sulfammox), respectively. However, how to remove NH4+-N and SO42- together from leachate is unclear. In this study, NirAnammox and Sulfammox cooperatively achieved nitrogen and sulfate removal from leachate using a biological process at low temperature (14–15 °C). NH4+-N, total nitrogen (TN), and SO42- concentrations in the influent were 610–700, 670–900, 1870–1920 mg/L, respectively, and 10 ± 1, 35 ± 3, and 897.7 ± 10 mg/L, respectively, in the effluent. Sulfammox, and NirAnammox removed 51.84% and 8.48% of the NH4+-N, respectively. However, 19.05% of NH4+-N was converted from NH4+-N to NO2−-N, which provided an electron acceptor for NirAnammox. Therefore, because leachate contains high concentrations of NH4+-N and SO42-, NirAnammox and Sulfammox can easily occur together, with nitrogen removal by Sulfammox being more than 3 times that of NirAnammox. The relative abundance of dominant bacteria of the Sulfammox were 10–20 times that of Candidatus Kuenenia (NirAnammox) in each reactor. Organic matter negatively affected NirAnammox, but not Sulfammox. Dissolved oxygen negatively affected both.