Dual stage PRO power generation from brackish water brine and wastewater effluent feeds

• MSDSPRO process is applied for power generation and BW brine concentration.
• Power density was higher in MSDSPRO than in DSPRO and PRO processes.
• RSD increased with increasing draw solution TDS or hydraulic pressure decrease.
• Solute losses per unit of power generated were calculated as the ratio of Jsr/W.
• BW brine can be decreased by 18% after the PRO membrane treatment.

Multi-Stage pumping Dual Stage PRO, MSDSPRO, process was proposed for power generation and brine concentration using brackish water brine and wastewater effluent feeds in stages one and two of the process. MSDSPRO process showed high efficiency for power generation and brackish water brine concentration before disposal. Power density, reverse salt diffusion and brackish water recovery rate were calculated in stages one and two of the DSMSPRO process taking into account the phenomenon of concentration polarization. The results showed that the MSDSPRO process efficiency for power generation was considerable even at relatively low draw solution concentrations. At 73 g/L draw solution concentration, power density was 4 and 6.25 W/m2 in stages one and two, respectively. Reverse salt diffusion was found to increase with draw solution concentration and it was higher in stage two compared to stage one. The ratio of reverse salt diffusion to power density, Js-r/W (mol/Wh) was calculated to determine draw agent loss per unit of power generation in the MSDSPRO process. The results also showed that volume of brackish water brine decreased by 18% after the PRO membrane treatment. As such, MSDSPRO process can be applied for power generation and reducing the volume of brine waste for disposal which is particularly important in inland desalination.

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