Maximizing Nutrient Recovery from Anaerobic Digest Using Membranes

This research revolves around nutrient recovery from wastewater, specifically anaerobic digest (AD). AD was chosen as the primary feed sample because, ideally, this research could be tested and scaled up for real wastewater treatment plants where AD is prominent. AD collected from run-off and sewage systems contains potassium, nitrogen, and phosphorus, critical fertilizers' nutrients. However, the recovery of these nutrients are impeded due to the presence of other organic compounds. Compound separations boil down to charge and sized-based properties. Polyelectrolytes appeal to both charge and sized based differences in ions because of their pore sizes and alternating bilayer charges. This research focuses on designing polyelectrolyte-based nanofiltration membranes by analyzing the co-transport mechanism of organics and nutrient (NH4+, K+) ions through charged polyelectrolyte multilayer films for achieving simultaneous nutrient permeance and organic pollutant rejection. Current findings have indicated that surface charge predominantly facilitates nutrient permeance, while size-exclusion plays a vital role in retaining organic pollutants. Additionally, a unique ion desolvation based separation was observed where the membranes with covalent crosslinking enabled intra-nutrient (NH4+/K+) selectivity. This finding is currently being investigated further as both ions have the same hydrated radius, which with traditional size based separation, would not be achievable. This research aims to continue these investigations by comparing these findings when applied to real world feeds (AD).