Abstract
Forward osmosis (FO) is an emerging technology that has received much global interest due to its potential applications in wastewater reclamation and seawater desalination. One of the major challenges to overcome is the detrimental effects of concentration polarization (CP), which reduce the effective osmotic pressure driving force and thus decrease productivity of the FO process. In this study, pressure assisted osmosis (PAO) was investigated as a method to increase the effective driving force and water flux by combining an osmotic pressure driving force with an additional hydraulic pressure. Experiments were carried out to examine the efficiency of the PAO process using a bench-scale setup specially designed to prevent membrane deformation under the applied hydraulic pressure. Results showed that PAO water flux increased with increasing the applied hydraulic pressure in FO mode (i.e., active layer facing the feed solution). The measured water fluxes were in good agreement with predictions based on a model developed to describe the water flux in PAO operation. However, the PAO water flux was lower than model predictions in PRO mode (i.e., active layer facing the draw solution). This observation is attributed to the spacer 'shadow effect' and the resulting reduction in the effective membrane area by the spacers. The results also showed that reverse solute flux decreased with increasing the applied hydraulic pressure in both FO and PRO modes. Although applying hydraulic pressure to FO increases energy consumption, the higher water flux in PAO reduces the number of membrane modules for the FO process. In addition, control of the driving force is easier in PAO than FO, leading to flexibility in system design and operation. Based on these results, a possible combination of FO and RO system with PAO was proposed for allowing higher energy efficiency in seawater desalination.
| Original language | English |
|---|---|
| Pages (from-to) | 159-166 |
| Number of pages | 8 |
| Journal | Journal of Membrane Science |
| Volume | 465 |
| DOIs | |
| Publication status | Published - 2014 Sept 1 |
Bibliographical note
Funding Information:This research was supported by the World Class University (WCU) program (Case III) through the National Research Foundation of Korea and funded by the Ministry of Education, Science and Technology ( R33-10046 ) and a grant from the Fundamental R&D Program for Technology of World Premier Materials funded by the Ministry of Knowledge Economy, South Korea , and the National Research Foundation of Korea Grant funded by the Korean Government (MSIP) (2014, University-Institute cooperation program)
Keywords
- Forward osmosis (FO)
- Membrane orientation
- Pressure assisted osmosis (PAO)
- Reverse solute flux
- Water flux
ASJC Scopus subject areas
- Biochemistry
- General Materials Science
- Physical and Theoretical Chemistry
- Filtration and Separation
