Cost Optimization of Osmotically Assisted Reverse Osmosis

Area of Science:

• Environmental Science
• Chemical Engineering
• Water Treatment Technologies

Background:

• High-salinity brine desalination presents significant challenges for conventional methods.
• Osmotically Assisted Reverse Osmosis (OARO) is a promising multistaged membrane process for such applications.
• Optimizing OARO configurations is complex due to nonlinear performance and interconnected operational parameters.

Purpose of the Study:

• To develop a nonlinear optimization model for identifying minimum cost designs of OARO processes.
• To comprehensively evaluate the decision space for OARO configurations and operations.
• To minimize overall cost, considering both capital and operational expenditures.

Main Methods:

• Development of a nonlinear optimization model with a cost-minimizing objective function.
• Inclusion of nonlinear process performance and implicit relationships among process streams and stages.
• Evaluation of multistaged membrane processes, saline sweep cycles, and water recovery.

Main Results:

• Cost-optimal OARO designs typically minimize the number of stages and eliminate saline makeup streams.
• Purging from the first sweep cycle and decreasing stage membrane area/sweep flow rates are favored.
• Optimal configurations for 50-125 g/L TDS feed and 30-70% recovery yield costs <= $6/m³.

Conclusions:

• The developed model effectively identifies cost-effective OARO designs for high-salinity brine desalination.
• Future research should focus on membrane properties (structural parameter, burst pressure) and unit cost reduction.
• OARO offers a viable solution for treating challenging saline water sources at competitive costs.