Specific oxygen uptake rate (SOUR) is significant parameter to determine the microbial activity and examined the effluent quality in biological wastewater treatment. Chemical oxygen demand (COD) is the major indicator in monitoring the effluent quality in relation on its removal mainly depends on the microbial activity in the activated sludge. So, this research is conducted to study the effect of aeration rate on SOUR and determined the best oxygen requirement in removing COD in domestic wastewater. The procedure was carried out by using domestic wastewater as the seed sludge in sequencing batch reactor. The reactor with working volume of 2L was operating 6 cycles in 24 hours with five phases (feeding, aeration, settle, draw and idle). The aeration time is fixed to 2.5 hours. The dissolved oxygen and COD readings were recorded with four types of aeration rate adjusted at 1L, 2L, 3L and 4L / min daily for 7 days. The result indicates that, 3L/min gives the highest SOUR which reflects that the high activity of microbial in this condition. Besides, the effluent also shows the highest COD removal efficiency on 3L/min of aeration rate. So, as a conclusion the best oxygen requirement for the microbial to carry out their activities on aeration rate of 3L/min.
