Raw mixed pharmaceutical industry and domestic wastewater characteristics are such as BOD5 = 90-130 mg L(-1), COD = 200-300 mg L(-1), SS = 900 mg L(-1), pH = 6.4-6.8, T = 20 degrees C, NH3 = 26 mg L(-1), PO4(3-) = 8.5 mg L(-1). In treatment plant, the parameters such as BOD5, NH3, PO4(3-), SS, MLVSS, pH, temperature, sludge volume and microorganisms predominance are studied, under constant sedimentation time (30 min) against variable aeration times. As a second step, the same parameters are studied under the constant aeration time (4 h) against variable sedimentation times. Effluent concentrations from sequencing batch reactor (SBR) are determined BOD5 = 13-18 mg L(-1), COD = 25-37 mg L(-1), SS= 9-21 mg L(-1), pH = 7.3-7.6, TDF = 1-2, T = 23 degrees C, NH3 = 1 mg L(-1), PO4(3-) = 8.1 mg L(-1). At the end of 6 h of aeration time, the efficiency of BOD5 reaches to 83%. The efficiency of BOD5 reaches to 81% under a 4 h aeration time and at 90 min sedimentation time. As a result, the optimum treatment efficiency has been taken under 4 h of aeration time and of 60 min of sedimentation time.
