Freshwater is a vital yet depleting resource. The diminishing supply from climate change and pollution is incompatible with the increasing demand from human population growth, and thus billions of people will experience prolonged water insecurity in the 21st century. The emerging freshwater crisis may be stymied with desalination technologies that can sustainably expand the water supply. Reverse osmosis (RO) is the premiere desalination technology. RO desalination bifurcates feed water into potable permeate water and highly concentrated brine via a polymeric membrane. The brine solution gradually precipitates minerals upon the membrane surface which obstructs the flow of water and degrades the membrane efficiency. The mineral precipitation is called scaling and is a primary hindrance of RO desalination technologies. Research of scaling geochemistry is therefore necessary to improve the efficiency of RO and thereby increase the practicality of RO for rectifying water insecurity. This study presents a reactive transport simulation that predicts scaling during RO desalination. The simulation describes the one-dimensional flow of feed water through the feed channel of an RO module, where permeate is removed continuously through the length of the module. The model is executed in the open-source geochemical code PHREEQC, which possesses numerous keywords and functions that are optimized for the geochemical processes that describe reactive transport and desalination. The simulation was validated with literature of RO plants and was tested with a commercial RO module and with real water bodies to an error of 50%. A graphical user interface will be developed to improve accessibility of the computational tool for researchers. The simulation provides applied and fundamental value to experimental research that can ensure freshwater security for the 21st century and beyond.

A PHREEQC simulation of scaling during RO desalination

ACS Spring Meeting 2021

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