Dynamic computation of multicomponent water and nutrients transport in forward osmosis system

As aquaculture production garners more interest around the globe, the production of aquaculture effluent will continue to rise. With the presence of dilute nutrients (NH₄⁺ and H₂PO₄⁻) in the effluent, the recovery of said nutrients requires a dewatering process. Forward osmosis (FO) systems are good dewatering processes as they have low fouling tendencies and better reuse efficiency. With that, a method for performance simulation is required for multicomponent FO systems. Multicomponent Fickian solution-diffusion model provides a simple computation method for FO systems containing more than three ions. Preliminary experimental studies concluded that NH₄⁺ transport across FO membrane relies on self-diffusion and induced diffusion caused by draw solute (Mg²⁺). For H₂PO₄⁻ ions, the transport was mainly contributed by convection as the diffusion of H₂PO₄⁻ across FO membrane showed positive relation with increasing water flux. Experimental validation of estimated parameters was also performed by two separate experiments. FO system performance such as water flux, reverse salt flux, nutrient rejection, and final nutrient concentration was computed and compared with experimental data. The comparison showed that the values computed were generally within 6 % of deviation with some outliers at 9 % of deviation. Dynamic computation showed the flexibility of estimated parameters as it can also predict FO system performance that operates at longer operation period and a at a higher initial volume of feed and draw solution.