Synthetic wastewater containing wheat starch and different carbon sources were treated using sequencing batch reactor (SBR) in pilot scale. First, the effects of number of impellers, input mixed liquor suspended solid (MLSS), carbon source, and temperature were investigated on treatment ability, effluent quality, and sludge settlement properties by fractional factorial design (FFD). Impeller diameter would not show considerable effect on reactor performance. Next, the most important parameters were investigated within a response surface methodology (RSM) context. Removal efficiency (COD removal), effluent total suspended solid (TSS), and sludge volume index (SVI) were assessed as outputs. The determination coefficient (R2) value for COD removal, effluent TSS, and SVI were 0.9679, 0.9638, and 0.9744, respectively. In optimum condition, COD removal of 88%, TSS of 62 mg/L, and SVI of 55 mL/g were obtained.

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