PhD Proposal: Sahar Souizi

Nutrient pollution from agricultural and municipal waste threatens water quality and ecosystem health, and global phosphorus scarcity and energy-intensive nitrogen production underscore the need for circular nutrient economies. We propose Donnan dialysis, which leverages electrochemical potential gradients across ion-exchange membranes, to selectively recover nutrients from wastewater. Although flat-sheet Donnan dialysis reactors are useful for evaluating fundamental ion-exchange and transport behavior, this reactor configuration is not scalable and cannot support simultaneous recovery of anionic and cationic nutrients. My research aims to develop and apply advanced tube-in-tube Donnan dialysis reactors for scalable and simultaneous nutrient recovery from real waste streams by (1) developing a first-principles-based model to optimize nutrient recovery under variable batch-recycle conditions, (2) constructing modular tube-in-tube Donnan dialysis reactors with tubular ion-exchange membranes to enhance the rate of nutrient recovery due to the increased surface area, and (3) applying the reactors to poultry litter slurries to examine the effects of organic matter, particles, and competing ions on nutrient recovery and downstream precipitation of slow-release fertilizers, such as struvite and potassium struvite. My work will deliver mechanistic insights to ion transport in Donnan dialysis systems, demonstrate a scalable reactor design for sustainable nutrient recovery, and inform the design of robust, field-ready systems capable of sustainable nutrient recovery directly at the source.