Modeling and optimization of electrodialysis for nutrient recovery from wastewater

Municipal and agricultural wastewaters often contain excessive nitrogen and phosphorus, which can disrupt ecosystems through eutrophication. These nutrients frequently originate from synthetic fertilizers produced by costly and energy-intensive processes. Thus, recovering nutrients from wastewater has the potential to prevent ecological harm and improve agricultural economics simultaneously. Several experimental studies highlight electrodialysis (ED) as a promising method for recovering nutrients in concentrated form for reuse as fertilizer. However, existing modeling and optimization studies of ED primarily target water desalination and do not address the unique challenges of nutrient recovery or assess the viability of ED for this purpose. To address this gap, this paper presents detailed ED models, novel solution strategies and simulation tools, a novel cost optimization formulation, and extensive optimal design results for wastewater nutrient recovery. Using formal optimization algorithms revealed novel strategies for achieving high product concentrations and yielded significantly lower costs than designs based on common heuristics. Results indicate that ED can produce a 3.5 wt\% nitrogen product for under 150 \$/t-N. These metrics suggest that ED could play a key role in sustainable fertilizer production from wastewater, particularly when combined with other technologies for achieving higher concentrations. However, the current analysis has some important limitations that could degrade these figures in practice, which are also discussed.