Analysis of raw and pre-treated seawater for potential biofouling precursors

• Assess biofouling precursors in RO desalination plants
• Main biofouling precursors were TEP and microbial community composition.
• Microbes known to be involved in biofouling and TEP production were identified.
• Low nutrient levels and high N/P ratio provoked a higher TEP production by microbes.

Here, the biofouling precursors of raw and pre-treated seawater from a reverse osmosis (RO) feed tank were investigated using a lab-scale RO cross-flow system. The microbial communities, nutrients and TEP present in both source waters were analyzed using flow cytometry, light microscopy, flow cell injection and colorimetry. All biofilms formed were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and colorimetry. Evaluation of both seawater sources showed (1) low nutrient levels and a high N/P ratio known to provoke a higher TEP production by microbes, (2) the presence of microbes known to be involved in biofouling and transparent exopolymer particles (TEPs) production and (3) a high concentration of TEP known to provoke membrane biofouling.