Cost optimization models for emerging water treatment processes benefit from holistic assessment of an entire process, including considerations for pretreatment, which can be costly. Previous optimization models have not accounted for the impact of chemical phenomena that occur during water treatment, such as chemical reactions that occur during pretreatment and mineral scaling in membrane treatment processes.
Mineral scaling—the buildup of minerals in a membrane, affecting its performance—presents a critical challenge to achieving high water recovery rates. As researchers refine desalination designs, they must consider the cost tradeoffs of reducing mineral scaling with desalination processes. Modeling frameworks should account for many variables in addition to mineral scaling as high-recovery treatment trains are optimized.
NAWI researchers Oluwamayowa Amusat, Adam Atia, Tim Barthlomew, and Alexander Dudchenko developed a cost optimization modeling framework for the technoeconomic assessment of desalination systems with mineral scaling and precipitation incorporated. The work—published in ACS ES&T Engineering—details a framework that includes mathematical optimization of complex processes with detailed water chemistry predictions for phenomena like mineral scaling and precipitation.
NAWI’s framework is generalizable and is demonstrated through its application to hypothetical high-recovery treatment trains for brackish and seawater desalination, centered on high-pressure reverse osmosis (HPRO), an emerging technology that shows significant promise for advanced desalination applications. This is the first technoeconomic assessment to incorporate mineral scaling predictions and chemical pretreatment into HPRO optimization. The approach includes a technoeconomic assessment on a conceptual treatment train that includes chemical pretreatment—soda ash softening and recarbonation—and membrane-based desalination in standard and HPRO.
The framework anticipates pretreatment, cost, and operational requirements needed for high recovery desalination that is cost effective and feasible. Results show that the overall cost of treatment is dominated by the soda ash softening process, while a pH control step is needed to control calcium carbonate scaling, which is critical for reaching higher water recoveries in seawater and brackish water treatment. The findings indicate that more research into reducing the cost of scaling control is worthy of further investigation.
The research emphasizes the importance of a holistic approach to optimization design, where pretreatment and primary treatment considerations are incorporated as key elements for cost-optimal operation.