Rapid start-up and stable maintenance of partial nitrification-anaerobic ammonium oxidation treatment of landfill leachate at low temperatures.

The current research regarding anaerobic ammonium oxidation (anammox) for the treatment of landfill leachate mainly focuses on a temperature range of 30-35 °C. However, achieving and maintaining anammox at lower temperatures would widen its application for the treatment of landfill leachate. This study, attempts to address this issue by using a combined process involving an upflow anaerobic sludge blanket (UASB), anoxic/oxic (A/O) reactor, anammox reactor (ANAOR), and anaerobic sequencing batch reactor (ASBR) to enrich anammox bacteria at relatively low temperatures. The rapid start-up of the partial nitrification-anammox process for landfill leachate treatment was achieved and maintained at 13-22 °C. The experiment was divided into phase 1 (20-22 °C) and phase 2 (13-15 °C). The results showed that 87.1% of the chemical oxygen demand (COD), 97.4-97.7% of the ammonium nitrogen (NH4+-N), and 93.3-94.7% of the total nitrogen (TN), were removed. At least 29.3% and 11.4% of NH4+-N was removed through anammox in phases 1 and 2, respectively, with an accumulation NO2--N ratio of 86.1-88.6%. Candidatus Kuenenia was the dominant anammox bacteria in the anammox process. A low temperature of 13-15 °C did not affect ammonia oxidizing bacteria (AOB), and their relative abundance in the A/O reactor ranged from 27.29% to 33.22%.