Effect of seawater variability on endemic bacterial biofouling of a reverse osmosis membrane coated with iron nanoparticles (FeNPs)

•Biofouling study of endemic bacteria on iron nanoparticle coated membrane.•The Sea of Cortez water has a high potential to biofoul the Reverse Osmosis membranes.•Physicochemical parameters values of El Sol Beach water delay biofilm growth.•Temperature, pH and dissolved oxygen affect directly the biofilm growth.•Temperature, pH and dissolved oxygen improve iron nanoparticle coating effectiveness. Biofouling presents difficult problems for seawater reverse osmosis (SWRO). Although iron nanoparticles (FeNPs) exhibit anti-biofouling properties, this may vary with geographic location. The efficacy of an FeNP coating for SWRO membranes is studied at laboratory scale in two sites – Sea of Cortez, Mexico (27.917°N, 110.776°W), and El Sol Beach, Chile (33.01°S, 71.553°W) – with significant differences in physicochemical parameters. Constant concentrations (109CFU mL−1) of native strains Bacillus halotolerans MCC1 and Bacillus sp. TA011_2 (EU308309), were respectively used at each of the sites to promote biofouling. The biofilm thickness, total, viable and non-viable cell counts, and organic matter were analyzed. More biofouling (>74%) was observed at the Mexican site due to differences in temperature and pH, but the coating presented stronger biocide effect (by 29%) there. Temperature, dissolved oxygen and pH had a more significant effect than salinity on biofouling FeNP coated membranes.