Sequencing batch reactor technology (SBR) is an increasingly popular reactor configuration because of flexibility of operation in the treatment of domestic wastewater. However, the combined two stage anoxic-aerobic for further nitrogen removal has not been explored further. This study aims to determine the performance efficiency of two-stage anoxic-aerobic using sequencing batch reactor. 10 L of SBR reactor was operated twice daily. The system was operated on a 500 minutes cycle with 10 minutes of feeding, 300 minutes for reacting, 60 minutes of sedimentation, 10 minutes of decanting and 120 minutes for an idle period. Effluent quality (chemical oxygen demand (COD), ammoniacal nitrogen (NH4–N), total suspended solids (TSS)), particle size and sludge settleability have been analyzed over a period of 35 days of operation. Results shows that the overall efficiencies for COD, TSS and NH4–N were 93.8%, 98.4 % and 85.9%, respectively. In the lab scale SBR reactor unit, the 2 h anoxic/1.5 h aerobic period resulted in good process performance with COD, NH4–N and TSS removal of 66.0%, 78.5% and 59.4 %, respectively. Increasing the length of anoxic up to 1 h did not enhance the NH4–N removal with 4.5% in anoxic phase and 7.2% in aerobic phase. Sludge settleability became poorer as the ciliate species becomes rich. The particle size of the sludge was observed to increase from 117.743 μm to 127.310 μm. It is recommended that the duration of combined anoxic/aerobic periods should be optimized to achieve maximum performance and nutrient removal.
