Reuse of reverse osmosis membranes

Leader


Challenge

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.

Investigation

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.

Outcomes

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.

Future Direction

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”).

Partners

    

L-C partner logos


 

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

Related Project: Alternative disposal methods for end-of-life desalination membrane elements

Further Information

FR1 UNSW Reuse Summary Poster

Project Summary Poster – reusing membranes

WP-Backgrounds Lite by InoPlugs Web Design and Juwelier Schönmann 1010 Wien