Breakthroughs in membrane fouling

Leader

Challenge

The most common problem facing desalination is the adverse effect of biofouling on reverse osmosis (RO) membranes which causes a decrease in permeate flux and salt rejection. Previous research indicates that the organic foulants are predominantly polysaccharides and proteins, which condition the membrane surface allowing bacterial biofilms to form. The bacteria may then use organic foulants on the membrane to replicate, exacerbating biofouling by extracellular polysaccharide (EPS) secretion. Although the behaviour of model EPS foulants on flux decline has been investigated and key bacterial species identified by molecular profiling of membrane autopsies, the exact contribution of each is not well understood. Does the majority of EPS fouling RO membranes originate from the source water, produced by bacteria on the membranes themselves? Or from biofilms in other locations of the RO plant such as intake pipes or cartridge filters?

Investigation

Identify the source of the most problematic EPS and develop removal strategies i.e. filtration/selective capture or biofilm removal/disruption strategies. Identify which conditions increase EPS fouling of membranes and production using suitable model polysaccharides and biofilm‐forming bacterial isolates. Use forward osmosis as a simple testing platform for EPS fouling behaviour and compare with reverse osmosis.

Outcomes

Seasonal samples were collected over two years from the Perth Seawater and the Southern Seawater Desalination Plants in Western Australia. The microbial communities were identified and compared using rapid DNA sequencing methods. The microbes were able to be isolated and the EPS produced used to simulate membrane fouling in the laboratory. Three types of fouling were investigated, examining the effect of salt concentration, pH, temperature and flow rate on the rate of membrane fouling. The conditions which affected fouling were identified and several breakthroughs made in understanding how these compounds contribute to fouling.

Chemical compounds which act to reduce EPS viscosity were tested in bench-scale reverse osmosis systems and found to reduce membrane fouling even at low concentrations by up to 30%. A new approach to alleviate membrane fouling using free radical generating compounds was discovered.

Future Direction

The collaboration with the partners will continue with grant applications submitted to fund future investigations into the anti-fouling effect of the novel free radical generating compound.

Partners

Ho partners

 


 

Total Value: $719,000 (cash and in-kind contributions)

Principal Investigator: Professor Goen Ho

Title: Control of organic membrane fouling through limitation and control of extracellular microbial products

Length: 27 months

Personnel: 11 collaborators contributing 4.8 FTE

Further Information

  • 2016. Nagaraja, N. Control of organic membrane fouling through limitation and control of extracellular microbial products. PhD thesis, Murdoch University.
  • 2016. Xie, J. Polysaccharide fouling in reverse osmosis and forward osmosis desalination and its alleviation. PhD thesis, Murdoch University. 
  • 2014. Singapore International Water Week. Singapore.
  • 2013. 2nd Water Research Conference. Singapore.
  • 2013. NCEDA Project Review Meeting. Perth, Australia.
  • 2013. 9th International Conference on Biofilm Reactors. Paris, France.
  • 2012. EBCRC Technical Review Meeting. Murdoch, Australia.
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