Sequencing batch reactor process for the removal of nitrogen from anaerobically treated domestic wastewater

This work presents the performance of a sequencing batch reactor (SBR) system used as a means of removing nitrogen from domestic wastewater containing a low chemical oxygen demand (COD) to nitrogen ratio due to pre-treatment with an anaerobic reactor. The aim of the work was to determine the feasibility of this system for the removal of nitrogen from the domestic wastewater. An SBR with a working volume of 5 L was investigated at different cycle times of 12, 8 and 6 h, at 18 °C. The efficiency of the SBR varied together with the duration of the cycle, where the optimum performance was seen in the 6 h cycle with the anoxic-aerobic-anoxic sequence. Due to the low quantity of organic matter present in the domestic wastewater after the anaerobic treatment, an additional supply of external carbon was necessary before the second anoxic stage. The removal efficiencies obtained were: 98% for total Kjeldahl nitrogen, 84% for total nitrogen and 77% for soluble COD. The reactor was thus shown to be viable, and it was concluded that this process may be successfully applied as a post-treatment for the removal of nitrogen from anaerobically treated domestic wastewater.