For energy-efficient wastewater treatment, many studies have focused on achieving autotrophic nitrogen removal through anaerobic ammonium oxidation (anammox), which is able to oxidize NH4+ to N2 with NO2− as the electron acceptor.1 To obtain nitrite as substrate, anammox is usually combined with partial nitritation (PN), reducing the requirements of aeration by 60% and organic carbon by 100%, and decreasing sludge production by 90%.2−4 It should be noted that 11% of nitrogen is converted to nitrate by the anammox reaction and the existence of nitrite oxidizing bacteria (NOB) inevitably aggravates nitrate accumulation in the effluent.2,5 However, the PN/anammox process is not able to remove nitrate contained in the wastewater, resulting in a relatively poornitrogen removal efficiency (51−87%).6