Interactions of operational parameters for brewery wastewater treatment using aerobic granular sludge

With more stringent environmental regulations on wastewater effluent quality, efficient and sustainable treatment solutions for the brewing industry are increasingly critical. This study evaluated the impact of influent chemical oxygen demand (COD) and hydraulic retention time (HRT) on the treatment of high-strength brewery wastewater using the aerobic granular sludge (AGS) biotechnology. A 2² full factorial experimental design with a replicated center point was utilized to assess the effects of COD (3000, 4000, and 5000 mg/L) and HRT (10.67, 12.8, and 16 h) on the removal efficiencies of COD, ammonia, and phosphorus. Regression analysis was conducted using Design Expert software and visualized through scatter plots to model the relationships between these operational parameters and the responses (treatment performance). The results show consistently high COD removal efficiency, exceeding 99% across all experimental runs with minimal variation. Due to this consistency, the selection of effective conditions focused only on ammonia and phosphorus removal performance, with the highest efficiencies achieved at an HRT of 16 h. Specifically, Run 1 (COD: 2900 ± 180 mg/L; HRT:16 h) achieved 96% ammonia removal and 96% phosphorus removal, while Run 2 (COD: 5050 ± 140 mg/L; HRT: 16 h) achieved 98% ammonia removal and 90% phosphorus removal. Regression analysis revealed key trends, where ammonia removal efficiency showed a strong positive relationship with HRT, but a negligible relationship with influent COD. Phosphorus removal efficiency exhibited a moderate positive relationship with HRT, and a weak negative relationship with influent COD. COD removal efficiency showed a negligible relationship with HRT, and a weak negative relationship with influent COD. Additionally, pH was observed to influence nutrient removal, particularly ammonia, as it affects microbial activity in AGS systems. Variations in pH likely contributed to the incomplete nitrification and nitrite buildup, indicating that pH should be a critical factor for optimization in future studies. These findings underscore the dominant role of HRT in enhancing nutrient removal and provide a foundation for improving AGS system efficiency in treating brewery wastewater. Future studies should focus on validating the results using real brewery wastewater, assessing long-term AGS stability, controlling the pH to enhance nitrification, and exploring resource recovery from AGS sludge to enhance sustainability.