Reverse osmosis (RO) membranes are now core to modern desalination processes and are widely used. These membranes usually need to be replaced every 5-8 years (several times in a plant’s lifetime), with typical replacements being in the order of one thousand membranes for each 10 mega litre per day (MLD) of installed product water capacity. As a result, the recent development of desalination plants based on RO technology in Australia will undoubtedly lead to a significant increase of the amount of spent membranes. At present the only option is to dispose of the used membranes in landfill which results in increased pressure on landfill utilities and is environmentally unsustainable going forward. Minimisation of these impacts is possible by increasing the lifecycle of the membranes by secondary use or material reuse.
Conduct a thorough review of the current information relating membrane and material reuse, recycling and disposal. Test the possibility of converting used membranes into porous ultrafiltration (UF) like membranes by removing the top polyamide layer using an oxidative process, leaving the second polysulfone layer intact. Investigate the possibility of disposing of membranes in electric arc furnaces for steelmaking, which would utilise the polymer material as a coke substitute reducing the amount of coke required and safely disposing of the membranes. Develop a comparative life cycle assessment (LCA) tool to assess all the inputs and emissions of all stages of a membrane’s lifecycle, including manufacturing and disposal, to determine the total environmental burden. By using this technique to compare the various proposed disposal options, informed decisions can be made about which option is the most environmentally sustainable.
Two main methods are proposed for reusing membranes, the first involves directly reusing the membranes after cleaning, and the second involves chemical treatment of the membrane surface to alter its performance. After the removal of the top polyamide layer of the membrane, the second polysulfone layer was shown to have a similar performance to commercially available UF membranes, therefore allowing for their potential reuse in UF applications.
Over 90% of the materials in used membranes were found to be suitable for use in electric arc furnaces however, manual dismantling to remove the unsuitable components and significant washing was required to remove contaminates. Together with the other suitable end-of-life options, such as incineration and syngas production, the amount of membrane material to be discarded can dramatically be reduced.
An end-of-life decision tool was developed (MemEOL) allowing membrane users to make informed decisions on the best course of action based on economic and environmental factors. The tool uses information on the location and condition of the end-of-life membranes, and assesses if it is suitable for direct reuse or conversion. Alternatively, if the membranes performance is outside of a usable range, the decision tool suggests the optimum alternative disposal option based on availability and location.
Further investigations will be done focusing on the reuse or recycling of valuable materials for other industries. A basic algorithm will be made available to provide recommendations to the users on the most environmental-friendly options. This will also provide an interface between current users and persons seeking second-hand membranes (i.e. a “membrane bank”).
Total Value: $812,800 (cash and in-kind contributions)
Principal Investigator: Associate Professor Pierre Le-Clech
Title: Reuse of reverse osmosis membranes
Length: 42 months
Personnel: 7 collaborators contributing 2.3 FTE
- 2015. Lawler, W. Assessment of End-of-Life Opportunities for Reverse Osmosis Membranes. PhD thesis, University of New South Wales.
- 2014. Lawler, W., et al. Comparative Life Cycle Assessment of End-of-life Options for RO membranes. Technical report available from NCEDA on request.
- 2013. Lawler, W., et al. Production and characterisation of UF membranes by chemical conversion of used RO membranes. Journal of Membrane Science 447 (0):203-211.
- 2013. 7th IWA Specialised Membrane Technology Conference and Exhibition for Water and Wastewater Treatment and Reuse. Toronto, Canada.
- 2013. NCEDA Research Showcase. Perth, Australia.
- 2013. NCEDA Project Review Meeting. Perth, Australia.
- 2013. NCEDA International Desalination Workshop. Melbourne, Australia.
- 2013. 8th International Membrane Science and Technology Conference. Melbourne, Australia.
- 2012. Rodricks, J. Re-use of RO membranes as low-pressure decentralised water treatment. Honours thesis, University of New South Wales.
- 2012. Lawler, W.,et al. Towards new opportunities for reuse, recycling and disposal of used reverse osmosis membranes. Desalination 299(0): 103-112.
- 2012. New coalition to coordinate research on membrane disposal. Desalination and Water Reuse Quaterley.
- 2012. Singapore International Water Week. Singapore.
- 2012. Membrane Technology Speciality Group IWA Regional Conference. Buenos Aires, Argentina.
- 2012. Lawler, W. Used RO membrane recycling in EAF steelmaking. Technical report available from NCEDA on request.
- 2012. Lawler, W., et al. What are the options for disposal of old RO membranes? Desalination & Water Reuse.
- 2011. Lawler, W., et al. Reuse of Old Reverse Osmosis Membranes. AWA Water Magazine: 76-77.
- 2011. 2nd Early Career Researcher Membrane Symposium. Glenelg, Australia.
- 2011. International Desalination Association World Congress. Perth, Australia.
- 2011. Sustainable materials, processes & technologies: Future pathways for reducing greenhouse gas impacts of materials. Sydney, Australia.
- 2011. Lawler, W. A review of the Product Stewardship Bill 2011 and how it applies to the reuse, recycle and disposal of reverse osmosis membranes. Technical report available from NCEDA on request.