Reverse Osmosis (RO) desalination is an important step of wastewater reuse as it can remove salts and trace contaminants. However, RO also generates a lot of high salinity brine that needs to be dealt with. Membrane distillation, a process not affected by the salinity of water, provides a way to extract water from this brine with high water recovery and has been proposed as a solution for RO brine management. However, pore wetting of membranes in membrane distillation is one of the major hurdles that prevents its implementation in treatment trains. Amphiphilic organic compounds present in wastewater are known to be the cause of membrane wetting. The objective of our study is to identify a pre-treatment strategy that can prevent membrane wetting in membrane distillation of RO brine. We compare three different pre-treatment strategies with different separation mechanisms, namely foam fractionation, advanced oxidation, and ultrafiltration; each of these treatments will lead to diverse wetting behavior. We compare the change in conductivities on the distillate side for each pre-treatment and identify the most effective pre-treatment. Promising results with respect to reduction of pore wetting have been found when pretreating the RO brine with foam fractionation. We analyzed the composition of the organic matter before and after pre-treatment to understand the nature of the compounds that removed by each treatment. This understanding of pore wetting in complex waters, such as wastewater RO brine, will help implement MD as a treatment strategy for brine management in desalination systems.

Pore wetting in membrane distillation treatment of wastewater reverse osmosis concentrate: Causes and prevention

2019 Fall National Meeting

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