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Biofouling on reverse osmosis membranes

Arnaud, Damien (2015) Biofouling on reverse osmosis membranes. Honours thesis, Murdoch University.

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Membrane biofouling is a major concern in water treatment processes as it can significantly reduce the system’s efficiency. Biofouling is mainly caused by microorganisms, and is difficult to control or avoid. It leads to higher operating pressure which strains the membrane, shortens the membrane life, and increases maintenance costs.

Multiple literature reviews suggest that the main contributors to membrane biofouling are polysaccharides. This is why in this project two model polysaccharides (alginate and xanthan) were used to study their individual fouling effects on reverse osmosis efficiency, as well as their fouling effects coupled with calcium chloride on the same system’s efficiency. During experiments, the polysaccharides were used in 0.2g/L concentrations, while calcium chloride was used at a concentration of 1.3mM. Because alginate and xanthan are two different types of polysaccharides, they would be expected to have different physical and chemical properties and thus have different fouling behaviours.

It was found that the polysaccharides did not have much effect on the system’s efficiency in the absence of calcium chloride. In experiments where calcium chloride was added in the feed solution with the polysaccharide, it was demonstrated that the addition of salt led to increased membrane fouling and greater decreases in system efficiency.

The fouled membranes were kept for confocal laser scanning microscopy of the fouling layers. The images determined the general structure of the cake formed on the membrane. Using the Imaris software, calculations on the average volume the cake layer was occupying (bio-volume) and the average compactness of the cake layer could be done.

During experiments, the membrane showed good salt rejections with over 96% salt rejection for each experiment

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Engineering and Information Technology
Supervisor(s): Li, Linda, Ho, Goen and Skillman, L.
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