Abstract
Using anammox as a novel biological process for nitrogen removal from wastewater containing high concentrations of ammonium has attracted much attention. This study focuses on the potential for removing nitrogen from reject water in a municipal wastewater treatment plant using a combined nitritation/anammox process with fixed-bed reactors. In a bench-scale plant that was fed reject water, the nitrite conversion efficiency was above 80% for about 210 days during the nitritation operation. Nitrate production was negligible during this period. We found that the NO2--N/NH4+-N ratio of the anammox reactor influent could be maintained easily by controlling the flow rate of bypass wastewater according to the nitritation performance. For the anammox reactor, significant nitrogen removal was observed immediately after the start-up and a maximum nitrogen removal rate of 2.9 kgN·m-3·d-1 was obtained 80 days after start-up. When the influent ammonium concentration was fluctuated intentionally during the experimental operation, the performance of the combined nitritation/anammox process was almost constant and the average nitrogen removal efficiency was 81%.
