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Pressure enhanced fouling and adapted anti-fouling strategy in pressure assisted osmosis (PAO)
Blandin, G.; Verliefde, A.R.D.; Le-Clech, P. (2015). Pressure enhanced fouling and adapted anti-fouling strategy in pressure assisted osmosis (PAO). J. Membr. Sci. 493: 557-567.
In: Journal of Membrane Science. Elsevier: Amsterdam. ISSN 0376-7388; e-ISSN 1873-3123, more
Peer reviewed article  

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Author keywords
    Forward osmosis; Pressure assisted osmosis; Hydraulic pressure; Organic fouling; Osmotic backwash

Authors  Top 
  • Blandin, G., more
  • Verliefde, A.R.D., more
  • Le-Clech, P.

    The concept of pressure assisted osmosis (PAO) has proven to be promising to tackle current flux limitations in forward osmosis (FO), but implementation of this concept in practice requires further research, especially in the context of wastewater reuse, for which organic fouling normally occurs. This study focuses on the impact of pressure addition in the PAO operation and on the assessment of the respective impact of osmotic and hydraulic driving forces on fouling behavior in accelerated fouling conditions. The evidence that the application of moderate hydraulic pressure (4 bar) lead to more severe fouling phenomena in PAO process was clearly demonstrated. Foulant cake compaction due to the applied pressure resulted in detrimental additional resistance to water permeation, thus impacting filtration flux. A high cross flow velocity (CFV) cleaning strategy, already proven to be effective for FO operation, was shown to be inappropriate for PAO. The efficiency of osmotic backwashing to clean membranes after PAO operation was extensively evaluated for both membrane orientations. The results demonstrated that the specific combination of osmotic backwashing with subsequent water flushing used in this study cleaned effectively the highly fouled membrane. Importantly, osmotic backwash also allowed for complete cleaning of the membrane support layer when using the membrane with the support layer facing the feed, thus tackling previously irreversible fouling phenomena, and potentially enabling FO/PAO operation in both membrane orientations in practice. Finally, a mechanistic model to illustrate fouling and cleaning in PAO was proposed.

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