Generating Osmotic Power Using Waste Effluents for Pressure-Retarded Osmosis

Abstract

Pressure-retarded osmosis (PRO) has a chemical potential to generate sustainable energy by utilising a semi-permeable membrane. RO-brine management with effluents being disposed of and energy usage are two issues that RO systems and deionised units face. The energy generation using the PRO techniques is proposed to address both of these issues practically. PRO can be used and integrated with the configuration of RO-brine as draw solution (DS) and effluent from demineralisation unit as feed solution (FS) that may generate the osmotic power density when it is applied. In this study, osmotic pressure for DS and FS was computed experimentally to predict \({\text{W}}_{\text{p}}\) of the PRO, and the performance of the PRO process was evaluated using various scenarios, which included the spatial process parameters of applied pressure, concentrations and flow rates for DS and FS. In this approach, the effluent solutions could serve as an inflow source. Additionally, there is no need for pre-treatment of the DS and FS, as is required in the common PRO system. Experiments were conducted to estimate the transport properties of commercial SW-membranes. Based on these experimental scenarios, trials were conducted using three DS of NaCl concentrations of ~ 51.8, 44.1, and 36.2 g/L to investigate the viability of the PRO, where the largest \({\text{W}}_{\text{p}}\) reached 2.83, 2.32, and 1.94 W/m², while the smallest \({\text{W}}_{\text{p}}\) was 1.5,1.18, and 1.0 W/m², and the flux reversal point of the \({\Delta \text{p}}_{\text{PRO}}\text{ was}\)~10.8 bar and 9.4 bar, corresponding to the different flow rates. Additionally, the effects of dilution on the system were also observed.