Membrane backwash cleaning using CO2 nucleation

Mohanned Al Ghamdi, Abdulsalam Alhadidi, NorEddine Ghaffour

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Low pressure membranes, such as ultrafiltration (UF), are widely used in water treatment applications, including the pretreatment of reverse osmosis desalination. UF membranes produce a water of superior quality, in addition to reducing the footprint and the use of chemicals, compared to conventional methods. However, membrane fouling remains a major drawback, and frequent membrane cleanings are required to maintain the flux of water and its quality. Typically, after a series of backwashes using an UF permeate, a chemical cleaning process is applied to fully recover the membrane's permeability. However, frequent chemical cleanings negatively affect the lifetime of the membrane, the environment, and increase operational costs. Here, we introduce a novel cleaning method that uses a solution saturated with CO2 to clean the membranes through the backwash step. As the pressure drops, the CO2 solution becomes supersaturated, and bubbles start to nucleate within the membrane pores and on its surface, resulting in the effective removal of the deposited fouling material. These foulants are further helping the nucleation process as they are considered as imperfection sites with high creation and growth of bubbles. Investigations performed for different synthetic feed solutions of organic compounds (sodium alginate), colloidal matter (silica) and sea salts, at different concentrations, show that our new physical cleaning process using CO2 is more performant than the regular backwash using Milli-Q water. We obtain a 100% flux recovery, in a short time, even under severe irreversible fouling conditions. Based on these results, we conclude that replacing water by a solution saturated with CO2 for the backwash cleaning of filtration membranes provides significant benefits to existing cleaning processes, and represent a promising alternative for improving and lowering the frequency of conventional chemical cleaning methods.
Original languageEnglish (US)
Pages (from-to)114985
JournalWater Research
Volume165
DOIs
StatePublished - Aug 13 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The research reported in this paper was supported by King Abdullah University of Science and Technology (KAUST), Saudi Arabia. Authors extend their gratitude to the Water Desalination and Reuse Center (WDRC) lab staff for their support. The authors would also like to thank Xavier Pita, Scientific illustrator at KAUST, for creating Fig. 7.

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