National Natural Science Foundation of China (No. 52170096)

Sulfate-dependent ammonium oxidation (Sulfammox) is a promising technology for treating high-concentration sulfate-ammonia wastewater. By utilizing SO4^2- as an electron acceptor and NH4+ as an electron donor, Sulfammox can simultaneously convert both NH4+ and SO4^2- in a single reactor, offering advantages over conventional biological treatment methods, such as reduced energy consumption and treatment costs. However, the removal efficiency of NH4+ and SO4^2- in Sulfammox is often unstable. To address this limitation, this study proposes using both nitrite (NO2-) and SO4^2- as electron acceptors for ammonia oxidation, aiming to enhance simultaneous sulfur and nitrogen conversion in a hybrid bioreactor. To investigate this, we designed two expanded granular sludge bed (EGSB) reactors: one for Sulfammox and another for a hybrid bioreactor of Anammox + Sulfammox, operating continuously for 151 days. The objectives of this study were: 1) to elucidate the mechanisms behind Sulfammox intensification in hybrid systems and identify key microbial species; 2) to explore the metabolic pathways of the Anammox + Sulfammox hybrid systems through metagenomic analysis. This study provides the metagenomic sequences of potential species for Sulfammox utilizing SO4^2- as an electron acceptor, as well as for Anammox + Sulfammox utilizing both SO4^2- and NO2- as co-electron acceptors. The findings offer new insights and strategies for the efficient treatment of high-concentration NH4+ and SO4^2- wastewater, with significant theoretical and practical implications.