Leachate was sampled from a landfill in Japan that had been in operation since 1973. Municipal solid waste and industrial waste, such as fly ash, bottom ash and excess sludge, had been disposed in this landfill. The leachate was delivered to the laboratory in closed containers every 2 months and was stored at 5 °C until use. The characteristics of the landfill leachate are shown in Table 1. Because ammonium concentration in the influent changed with the seasons, the leachate was diluted to maintain ammonium concentration at 150–200 mg/L.