Pilot-scale evaluation of ammonia recovery from anaerobic digestion leachate using a membrane contactor: Performance optimization and practical feasibility assessment

초록

Ammonia recovery from anaerobic digestion (AD) leachate has gained increasing attention as a sustainable strategy for nutrient recycling and energy-efficient wastewater treatment. However, most previous studies have been limited to lab-scale investigations, and the practical feasibility of membrane contactor (MC) systems under real wastewater conditions remains insufficiently understood. In this study, a pilot-scale MC process for ammonia recovery was developed and evaluated using real AD leachate. The system was designed based on a theoretical modeling framework, and key operating parameters were quantitatively assessed using SHapley Additive exPlanations (SHAP) analysis. The process was subsequently optimized through synthetic solution experiments, achieving a maximum ammonia recovery of 96.38% under a serial module configuration. While a feed pH of 12 yielded the highest ammonia recovery under synthetic conditions, a feed pH of 10 was selected as the practical operating condition for real AD leachate to reduce chemical consumption and inorganic scaling. Operation with real AD leachate was then conducted under the selected practical conditions, and a preliminary operating-cost assessment was performed. By applying a pilot-scale antiscalant dosing strategy, an extended multi-day operation was successfully sustained for up to 176 h, concentrating the recovered ammonia to 9613.2 mg/L as NH4+-N in the acidic collector. In addition, the limits of cleanability and the factors contributing to performance deterioration were explicitly investigated to provide practical guidelines for real-world application. In conclusion, this study presents the pilot-scale application of an MC system for ammonia recovery, integrating theoretical modeling, parametric analysis, and real AD leachate operation. The results demonstrate the technical feasibility of MC-based ammonia recovery from real AD leachate and highlight key operational challenges and design strategies for full-scale implementation.

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