Novel Thermal Desalination Brine Reject-Sewage Effluent Salinity Gradient for Power Generation and Dilution of Brine Reject

Salinity gradient resource presents an essential role for power generated in the process of pressure-retarded osmosis (PRO). Researchers proposed several designs for coupling the PRO process with the desalination plants, particularly reverse osmosis technology for low-cost desalination but there is no study available yet on the utilization of the concentrated brine reject from a thermal desalination plant. This study evaluates the feasibility of power generation in the PRO process using thermal plant brine reject-tertiary sewage effluent (TSE) salinity gradient resource. Power generation in the PRO process was determined for several commercially available FO membranes. Water flux in Oasys Forward Osmosis membrane was more than 31 L/m2h while the average water flux in the Oasys module was 17 L/m2h. The specific power generation was higher in the thin film composite (TFC) membranes compared to the cellulose triacetate (CTA) membranes. The specific power generation for the Oasys membrane was 0.194 kWh/m3, which is 41% of the maximum Gibbs energy of the brine reject-TSE salinity gradient. However, the Hydration Technology Innovation CTA membrane extracted only 0.133 kWh/m3 or 28% of Gibbs free energy of mixing for brine reject-TSE salinity gradient. The study reveals the potential of the brine reject-TSE salinity gradient resource for power generation and the dilution of brine reject

Impact of hydrodynamic conditions on optimum power generation in dual stage pressure retarded osmosis using spiral-wound membrane

The Dual Stage Pressure Retarded Osmosis technique is considered for power generation. The influence of feed flow rates, hydraulic pressure, and pressure drop on mass transfer and solute diffusion in a full-scale membrane model was investigated for the first time to maximize power generation. Dead Sea-seawater, Dead Sea-reverse osmosis brine, reverse osmosis brine-wastewater, and seawater-wastewater salinity gradient resources were investigated for power generation. Results revealed a 71.07% increase in the specific power generation due to the dual-stage pressure retarded osmosis process optimization using Dead Sea-seawater salinity gradient resources. The increase in the specific power generation due to the dual-stage pressure retarded osmosis optimization was 108.8%, 63.18%, and 133.54%, respectively, for Dead Sea-reverse osmosis brine, reverse osmosis brine-wastewater, and seawater-wastewater salinity gradient resources. At optimum operating conditions, using the dual-stage pressure retarded osmosis process as an alternative to the single pressure retarded osmosis process achieved up to a 22% increase in the energy output. Interestingly, the hydraulic pressure at optimum operating conditions was slightly higher than the average osmotic pressure gradients in the dual-stage pressure retarded osmosis process. The study also revealed that power generation in the dual-stage pressure retarded osmosis process operating at constant mass transfer and solute resistivity parameters was overestimated by 2.8%

Pressure Retarded Osmosis: advancement, Challenges and Potential

An excessive amount of renewable energy could be possibly produced when solutions of dissimilar salinities are combined simultaneously in a semipermeable membrane. The aforestated energy harnessing for transformation into power could be achieved through the pressure retarded osmosis (PRO) process. The PRO system utilizes a semipermeable membrane for separating a low concentration solution from a pressurized-high concentrated solution. This work examines the recent developments and applications of the PRO process and potential energy that could be conceivably harvested from salinity gradient resources in a single-stage and multi-stage PRO processes. One of the existing challenges for this process is finding a commercial membrane that combines characteristics of the forward osmosis membrane (for reducing the phenomenon of concentration polarization) and the reverse osmosis membrane (to withstand high hydraulic pressure). For addressing this challenge, details about the commercial PRO membranes and the innovative laboratory fabricated PRO membranes are introduced. The potential of the PRO process is presented by elucidating salinity gradient resources, the energy of Pretreatment, the process design, PRO-desalination systems, and dual-stage PRO (DSPRO). It is anticipated that this paper can assist in widely understanding the PRO process and thus deliver important data for activating additional research and development