Response surface methodology approach for simultaneous carbon, nitrogen, and phosphorus removal from industrial wastewater in a sequencing batch reactor

Wastewater reclamation involving a sequencing batch reactor (SBR) has received more attention recently due to its high nutrient removal efficiency, cost-effectiveness, and low footprint. This study attempts to develop a stable and applicable activated sludge SBR for simultaneous carbon and nutrient removal from industrial wastewater. The derived-filed data were explored by response surface methodology (RSM) to identify the impact of operational variables on the SBR performance. Optimum conditions were obtained at 4000 mg/L MLSS, 100: 8: 2 COD: N: P ratio, 40 min/h aeration time, and 40 h cycling time, which resulted in the removal of 82.53% chemical oxygen demand (COD), 89.83% TKN, 87.23% PO₄^3--P, and 73.46% NO₃^--N. Moreover, the sludge volume index (SVI) and mixed liquor volatile suspended solids (MLVSS)/mixed liquor suspended solids (MLSS) ratio were 64.8 mL/g and 0.8, respectively. The maximum nitrification rate was calculated as 113.9 mg/L.d, which increased with the rise of the initial ammonium concentration. The specific denitrification rate (SDNR) was estimated in the range of 0.003-0.07 mgNO₃--N/mg MLVSS.d, depicting the high potential of the SBR reactor to eliminate nitrate by granular sludge. Accordingly, the removal efficiency of the optimized system revealed a notable capability towards meeting environmental regulations.