Coupling and modeling of electrically charged forward osmosis and membrane distillation for energy-efficient recovery of water and nutrient

Wastewater is increasingly recognized as a valuable resource for recovering clean water and nutrients. Membrane processes such as forward osmosis (FO) and membrane distillation (MD) are promising technologies for energy-efficient wastewater treatment but lack selectivity for nutrient recovery. Additionally, FO suffers from concentration polarization and reverse salt flux. To address these limitations, this study coupled electrically charged FO (eFO) and MD to enhance the recovery of both water and nutrients. After 24 h of batch operation, the coupled system operated under 1.5 V recovered 108 mL of clean water and 0.50 g struvite from synthetic livestock wastewater, which were 12 % and 233 % more than those of the control system, respectively. Increasing the eFO voltage and draw concentration significantly promoted water recovery and struvite production, while the MD temperature had negligible impacts on the system performance. A hybrid model was developed by integrating a mechanistic component and a support vector machine-based data-driven component. The mechanistic component of the model elucidated the voltage-dependent transport behaviors governing water and ion migration across the coupled eFO–MD system. The data-driven component of the model calibrated key operating parameters for the mechanistic component for accurate predictions of the recovery of water and struvite. The findings of the present study provide practical insights into the development and scale-up of novel membrane processes for recovery water and fertilizer from nutrient-rich wastewater.