Integrated alkaline electrolyser-pressure retarded membrane distillation system for ammonia wastewater valorisation: technoeconomic and environmental assessment

Ammonia is a major wastewater pollutant causing eutrophication, and reliable removal across broad concentration ranges is increasingly required. However, conventional treatment processes are limited in operational stability, applicable concentration range and energy efficiency, while integrated approaches enabling simultaneous ammonia removal and resource recovery remain limited. This study proposes an integrated alkaline electrolyser (AEL) and waste-heat-driven pressure-retarded membrane distillation (PRMD), directly coupling ammonia electrolysis-based removal with hydrogen production, freshwater generation and energy recovery. A mathematical model incorporating mass and energy balances and pressure drop equations was developed alongside technoeconomic and environmental assessments over influent ammonia concentrations of 5–1000 ppm, a range broader than that typically considered for conventional ammonia treatment. The integrated AEL-PRMD system achieves stable ammonia removal while producing 99.9% pure hydrogen up to 1.22 \(\times\) 10 −3 mol/s and 9.84 \(\times\) 10 −6 m 3 /s of freshwater. As ammonia concentration increases, the levelised cost of water rises from 5.5 to 12.4 $/m³, remaining comparable to thermal desalination, whereas environmental cost intensity decreases to 1.65 $/kg CO 2 -eq at 1000 ppm. These results demonstrate stable ammonia removal and resource recovery across a wide concentration range. Overall, the integrated configuration redirects wastewater treatment energy into valuable co-products, providing a flexible and energy-efficient platform for ammonia wastewater valorisation.