The contaminated liquid produced from rainfall seeping through the layers of waste in domestic landfill sites is known as leachate. Leachate from landfills is high in nitrogen content, mostly as ammonium, and is typically disposed of by transportation to a domestic wastewater treatment plant at a cost. Sequencing batch reactors (SBR) are compact fill-and-draw activated sludge systems that facilitate treatment in a singular reactor, including ammonium removal through nitrification. This study examines the viability of on-site SBRs nitrifying the high ammonium concentrations found in landfill leachate in New Zealand instead of transportation off-site. Two 1 litre volume SBRs were operated for over 6 months with increasing concentrations of ammonium in the feed to determine nitrification capacity. The reactors achieved significant ammonium removal at influent ammonium loading as high as 720 mg/L. The SBRs achieved ammonium removal efficiencies of 90% to 100% with a total suspended solids concentration of 17 to 18 g/L during the stable period of operation. pH control was required at higher influent ammonium loadings above 300 mg/L to prevent inhibition of the nitrifying bacteria by acidification. These results suggest that onsite SBR system can be made a viable option for leachate treatment in New Zealand .