Development of energy-saving volume retarded osmosis (VRO)-low pressure membrane (LPM) hybrid system for water treatment and identification of initial fouling mechanism in forward osmosis water treatment process.



Dr. Am JANG, a Professor from the College of Construction and Environmental System Engineering and Graduate School of Water Resources, and his research team have developed volume retarded osmosis (VRO)-low pressure membrane (LPM) hybrid system. The discovery of such novel process has lead to a publication of a paper in "Scientific Report (Impact factor=4.259, upper 16% of JCR journal in multidisciplinary sciences field)", a journal from the publishers of Nature, on November 6th, 2017 (online). Additionally, they have identified the initial organic fouling phenomenon that could occur in spiral-wound forward osmosis process at semi-pilot scale, with the use of real wastewater and the membrane surface analysis method. This lead to a publication in "Chemical engineering journal (primary author: Sung-Ju Im, phD student) (Impact factor = 6.216, upper 4.5% of JCR journals in chemical engineering field)", one of the most powerful and effective journals around the world, on November 2, 2017.



Forward Osmosis (FO) technology is a water treatment technology based on the osmotic pressure gradient of both solutions (feed and draw). It has been actively studied in academia and industry, and is considered as a substitute for reverse osmosis-based seawater desalination technology and a next-generation desalination technology. In general, since the forward osmosis technology requires a post-treatment technique for separating the draw solute from a high concentration of the draw solution, many researches and attempts have been made to develop an appropriate post-treatment technique. However, the high operating pressure (energy) of the post-treatment technology is pointed out as a limitation of the forward osmosis technology, and the development of a forward osmosis process that does not require post treatment, or post treatment with low or no energy requirement is urgently needed.



Through this research, Professor JANG and his research team, was the first to devise and develope a water treatment system design that can utilize the pressure to be used as the driving force for the low pressure membrane, via increase of draw solution volume in a closed tank. The value of this study is unmeasureably high, seeing as how the limitation of the existing osmosis process was improved, the possibility of practical use of the osmosis process was increased, and the direction of the new osmosis technology was suggested through this study. In addition, the spiral-would forward osmosis element is the most common form of the conventional element types, and it is similar to the reverse osmosis module that is used for seawater desalination. To date, the identification of the fouling phenomena of forward osmosis membranes has been limited to laboratory scale (Lab-scale) or to identifying them using model foulants. However, there are limitations in terms of operating conditions and structural characteristics of elements in order to apply the results to the actual process (element scale or pilot scale). Professor JANG’s research team determined the initial fouling mechanism, when spiral-wound forward osmosis element was used with wastewater as feed solution. The results of this study is very valuable, for it can help comprehensively understand the fouling mechanism of the forward osmosis, allow prediction of overall fouling phenomena in actual process, and help understand overall development of forward osmosis process.



Professor Am JANG, who conducted and led the study, said, "The results of this study have a great significance in overcoming the limitation of the forward osmosis process, a next generation water treatment technology. Not only it is significant, but the results from this study is also valuable, since understanding of the fouling phenomena is the key factor in development of forward osmosis technology. "

Based on the results of this study, Im Sung-Ju, a phD student and the first author of the published paper, presented at the International Desalination Workshop 2017, and was awarded by the Minister of Land, Transport and Tourism.



This study was carried out through researches on forward osmosis-reverse osmosis hybrid system, which is supported by Korea Agency for Infrastructure Technology Advancement, and through monitoring of irreversible foulants in the osmosis - based membrane process, supported by the research project of the Korea Research Foundation.



Titles of the published papers:

- New concept of pump-less forward osmosis (FO) and low-pressure membrane (LPM) process

- Organic fouling characterization of a CTA-based spiral-wound forward osmosis (SWFO) membrane used in wastewater reuse and seawater desalination