Membrane fouling, especially biofouling, is a major obstacle that hinders the efficiency of membrane filtration processes since it causes deterioration of both the quantity and quality of treated water, reduces membrane life and results in higher operational costs. One strategy to mitigate membrane fouling is modification of the membrane surface through increasing hydrophilicity, altering electrical properties or incorporating biocides. Despite these efforts, modified membranes can still suffer significant biofouling.
A naturally occurring polysaccharide with antifouling properties has been identified and could be used to combat membrane fouling. This polysaccharide was discovered during investigation of a fouled reverse osmosis membrane taken from a water treatment plant. The antifouling effect of the polysaccharide is potentially more effective than traditional antifouling methods due its ability to form unique hydrophilic coatings with heavily hydrated and randomly oriented chains.
Determine methods for immobilising the polysaccharide onto the surface of a membrane and investigate durability and antifouling effects. Optimise the coating process, including thickness and crosslinking density, to maximise water flux and antifouling capabilities.
A novel immobilisation method of crosslinking the polysaccharide onto existing RO polyamide membrane surfaces was developed and is the subject of a provisional patent application. Under realistic water treatment conditions, the coating was shown to be durable and exhibited exceptional antifouling properties. The coated membrane was found to have significantly higher surface hydrophilicity, high durability and attachment stability.
An optimised range of polysaccharide and crosslinker concentrations was determined and results from water flux tests showed that when the optimal range of coating composition was used for the coating, the water flux of the coated membranes was the same as that for the uncoated membranes. The coating was stable under a range of different pH, including those experienced during membrane cleaning. Critically, the coated membrane prevented significant biofouling compared to the uncoated membrane.
Scale up the polysaccharide coating technology to apply a uniform coating with suitable thickness over large areas of membrane surface. A pilot-scale trial of the coated membrane is also required to confirm the antifouling effect and test the water permeability ability of the coated membranes.
The technology is protected by a number of PCT patent applications. Further work is required in a number of areas that include scaling up of the application process, integration into a manufacturing facility and improving the efficiency of coating.
CSIRO is looking for commercial partners to assist in the development of pilot-scale testing to confirm the effectiveness of the coating and integrating the coating process either into the membrane manufacturing or in the post manufacturing phase.
Total Value: $757,418 (cash and in-kind contributions)
Principal Investigator: Dr Thuy Tran
Title: Mitigation of membrane biofouling using natural polysaccharide surface coating (Phase 1 and Phase 2)
Length: 12 months (Phase 1) and 11 months (Phase 2)
Personnel: 6 collaborators contributing 1.2 FTE and 5 collaborators contributing 1.1 FTE (Phase 2)