To research the performance of removing nitrogen and organics from old landfill leachate via denitrification-partial nitritation-ANAMMOX (DN-PN-ANAMMOX) process, an integrated reactor seeded with mature ANAMMOX sludge and nitritation sludge connected to a denitrification (DN) reactor was studied. The result showed that before the pre-denitrification reactor was connected, the PN-ANAMMOX reactor achieved a nitrogen removal rate (NRR) of 1.88 kg·(m3·d)-1 and a nitrogen removal efficiency (NRE) of 90.3% when the concentration of influent ammonia nitrogen and COD were 600 mg·L-1 and 483 mg·L-1, respectively. The NRR of the PN-ANAMMOX process dropped to 1.50 kg·(m3·d)-1 when the concentration of influent COD>483 mg·L-1, which corresponds to C/N>0.8. To relieve the influence of organic matter on ANAMMOX, a DN reactor was put in front of the PN-ANAMMOX reactor. The DN-PN-ANAMMOX process achieved an NRR and NRE of 1.37 kg·(m3·d)-1 and 98.6%, respectively, under the conditions of influent ammonia nitrogen and COD concentrations of 1100 mg·L-1 and 1150 mg·L-1, respectively. The NRR of ANAMMOX reached 15.6 kg·(m3·d)-1. The whole system realized a highly efficient and deep removal of nitrogen without any additional carbon source. When treating old landfill leachate, most of the biodegradable organics can be removed by the system.
Keywords: anaerobic ammonia oxidation (ANAMMOX); denitrification; landfill leachate; organic matter; partial nitritation.