Biofouling of reverse osmosis membranes: assessment by surface-enhanced Raman spectroscopy and microscopic imaging

Abstract

The decline in the performance of spiral-wound reverse osmosis (SWRO) membranes is frequently due to biofouling. This study focus on qualitative and quantitative diagnosis of SWRO membrane biofouling. Bacterial counts on the different surfaces of the fouled membranes were carried out. Surface enhanced Raman spectroscopy (SERS) was performed to highlight clogging materials as well as their natures and identity. The topography of the fouled membranes and the structures of biofilms were visualized by fluorescence microscopy (FM) and scanning electron microscopy (SEM). The results indicated the presence of bacteria in the different SWRO membrane areas. Those strongly adhered were significantly higher than those weakly. It varied between 26 × 10⁵ and 262 × 10⁵ CFU m⁻². However, SERS mapping showed different fouling levels and the thickness of the fouling layer was 5 µm. Microscopic imaging revealed biotic and abiotic deposits. These data can together allow better management of the seawater desalination process.

Keywords:

• Biofilm
• reverse osmosis membranes
• biofouling
• surface-enhanced Raman spectroscopy
• microscopic imaging

Disclosure statement

No potential conflict of interest was reported by the authors.

Acknowledgements

The authors wish also to thank Dayri Ahmed, director of the Souk T'lata seawater desalination plant, and Guermat Ismail, technical engineer, for their help and assistance.

Additional information

Funding

The authors are very thankful to the DGRSDT-MESRS - Algeria for their financial support.