Biofouling in reverse osmosis processes

Zaghy, Amar (2016) Biofouling in reverse osmosis processes. Honours thesis, Murdoch University.

Abstract

Reverse Osmosis (RO) is a water purification technology that uses a semi-permeable membrane to remove salt and other particles from drinking water. It is the dominant technology which has overtaken many conventional systems in recent years. Membrane biofouling is the main disadvantage of using RO technology which can result in reducing the system’s efficiency. The rejected microorganisms on the surface of the membrane form a fouling layer (biofouling) which leads to a decline in permeate flux, increase of hydraulic resistance, increase in operating pressure, and shortening of the membrane life. Polysaccharides, produced by microorganisms, are the main substances responsible for membrane biofouling. In this study, two types of polysaccharides (alginate and pullulan) were used to investigate their individual fouling effects as well as their fouling effects coupled with sodium chloride and calcium chloride. 50 mM of ionic strength (27.5 g NaCl + 1.47 g CaCl2) and 0.2 g/L of polysaccharides were used in the fouling experiments conducted with a laboratory-scale reverse osmosis system.

It was found that alginate lead to more reduction in system’s efficiency in comparison with pullulan. The effect of alginate on the efficiency of the system was much more severe in the presence of salt, namely sodium chloride and calcium chloride, compared to its individual effect in the absence of salt. The addition of salt led to an increase in membrane fouling and a decrease in system’s efficiency. On the other hand, it was found that pullulan enhanced the system’s efficiency when it is combined with salt.

To support the above findings, a Confocal Laser Scanning Microscopy (CLSM) analysis, a Total Organic Carbon (TOC) test, and an estimation of the weight of produced fouling layers were performed. In general, analysing the results of the tests supported the findings.

Item Type:	Thesis (Honours)
Murdoch Affiliation(s):	School of Engineering and Information Technology
Supervisor(s):	Li, Linda and Ho, Goen
URI:	http://researchrepository.murdoch.edu.au/id/eprint/33970

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