The WateReuse Association has published a report on research into the use of preformed chloramines to remove biofouling from seawater membrane surfaces.
The report, Pilot Testing Preformed Chloramines as a Means of Controlling Biofouling in Seawater Desalination – (09-09-1, 2012), looks at a project following up research done 30 years ago to resolve issues with the stability of chlorine residuals in the electrical power industry. This showed preformed chloramines react very slowly with the bromide in seawater.
The current project, led by Dr R Shane Trussell of Trussell Technologies, used a combination of bench-scale experiments and pilot testing to evaluate the use of preformed chloramines to control biofouling during seawater reverse-osmosis (RO) desalination.
Microbial analysis of the used elements showed little difference in biofilm density but demonstrated biofilm populations were different. This finding suggests chloramines do not prevent biofilm growth as much as they select the bacteria that live within that biofilm. Considering that the chloraminated RO train experienced less fouling, one possible conclusion is chloramine-resistant bacteria have characteristics that make them less likely to foul RO elements.