Marine bacterial biofilm formation and its responses to periodic hyperosmotic stress on a flat sheet membrane for seawater desalination pretreatment

Cartridge and membrane biofouling is a significant challenge for the seawater desalination industry. Current cleaning methods remain inefficient or potentially damaging to the membrane. This research characterized marine bacterial biofilm formation and further examined if periodic hyperosmotic shocks to the surface of a filter membrane would reduce bacterial biofilm and prevent membrane fouling. A lab-scale biofouling detector system was developed using an eight-channel pump to deliver simultaneous flow rates through eight 5 μm pore size, 25 mm diameter nitrocellulose membrane filters. A marine Alteromonas strain isolated from a desalination pilot plant was used as the model biofouling agent. The results showed the 30% NaCl shock produced a hyperosmotic stress that maintained the membrane permeability and flow rate while the control and DI H2O treated filters did not. Confocal Laser Scanning Microscopy results illustrated that the periodic 30% NaCl shocks slowed the biofilm maturation process by inducing cell mortality and reducing the biofilm thickness. Scanning Electron Microscopy results showed the salinity shock also reduced the coverage of extracellular polysaccharides in the treated biofilm matrix.

► The effectiveness of periodic 30% NaCl shock to reduce membrane biofilm was investigated.
► A biofouling monitoring system using marine Alteromonas was set up in a dead-end filtration mode.
► 30% NaCl treated filters maintained the flow rate, reduced biofilm thickness, and increased cell death.
► Microscopy investigations characterized the biofilm micro-channel systems and polymer matrix.