Cost optimization of low-salt-rejection reverse osmosis

Low-salt-rejection reverse osmosis (LSRRO) is an emerging membrane-based desalination technology for concentrating brines with potentially lower energy consumption and cost than thermally driven processes. We assess the technoeconomic performance of LSRRO by using an optimization model that minimizes the levelized cost of water (LCOW). We develop detailed models for the RO module and other equipment using WaterTAP (Water treatment Technoeconomic Assessment Platform), an open-source simulation and optimization software for water treatment. We improve upon previous LSRRO cost optimization studies by optimizing the salt permeability for each stage, which has significant implications for technoeconomic performance. We present the cost-optimal design, operation, and performance for three cases: 35 g/L TDS feed at 70 % recovery, 70 g/L at 55 %, and 125 g/L at 35 %. The cost-optimal LCOW and specific energy consumption (SEC) for these cases are 0.70, 1.89, and 7.41 $/m3 and 3.9, 8.4, and 30.4 kWh/m3, respectively. For each case, we use sensitivity analyses to provide guidance on key factors that impact economic viability. We also present the cost-optimal LCOW and SEC for feed concentrations between 5 and 220 g/L TDS and recoveries between 30 and 90 %. Lastly, we compare LSRRO to other high-salinity desalination technologies and find that it may be cost-competitive below feed concentrations of 125 g/L.

Automated summary

Low-salt-rejection reverse osmosis (LSRRO) is an emerging membrane-based desalination technology that can concentrate brines with potentially lower energy consumption and cost than thermally driven processes. Using an optimization model, we assess the technoeconomic performance of LSRRO and present cost-optimal designs, operations, and performance for different scenarios. We compare LSRRO to other high-salinity desalination technologies and find that it may be cost-competitive below certain feed concentrations.