Within the lifetime of most reverse osmosis (RO) systems some fouling will adversely affect membrane performance.One of the major foulants identified on lead membranes during a decade of membrane autopsy at the Genesys Membrane laboratory is biological fouling (biofouling).
All raw water sources contain microorganisms such as algae, bacteria and fungi. They also contain compounds which provide nutrients and energy sources which promote biological growth. In addition current methods of control such as chlorination will increase the availability of nutrient compounds.
The effects of biofouling on membrane operation include a reduction in flux, increase in pressure drop and salt passage and potentially membrane degradation and failure. Current technology favours the use of biocides to control biofouling; however bacteria in biofilm are more resistant to biocides than planktonic organisms. In addition using biocides produces an accumulated biomass which encourages active re-growth of the population. Therefore the successful approach must kill the biological population and successfully remove it from the membrane surface to prevent rapid re-growth.
This paper explores the processes for developing and testing a cleaning product Genesol 703 which removes biofouling from RO/NF/UF systems. The results of removing biofilm from membranes are presented. Product efficacy was determined by comparison of membrane flux rates before and after cleaning and visual inspection by scanning electron microscopy (SEM). The results demonstrate that Genesol 703 is a technically and economically viable cleaning chemical product for the removal of biofouling from membranes.
Removing biofilm from membranes – a practical approach