According to the International Desalination Association (IDA, 2017) there are more than 17,000 reverse osmosis desalination plants installed in more than 150 countries. In Spain, the Spanish Association for Desalination and Reuse (AEDYR) has registeres 950 facilities, taking into account small private plants, which makes Spain the fourth country in the world in capacity to produce desalinated water.
Periodically and after the loss of performance of the membranes, they are currently disposed of in landfills. It is estimated that around 800,000 membrane modules are discarded annually in the world (more than 14,000 tons of inert plastics).
Since 2014 and through the LIFE+ TRANSFOMEM project (LIFE13 ENV/ES/000751) "Transformation of disposed reverse osmosis membranes into recycled ultra- and nanofiltration membranes", the Membrane Technology group of IMDEA Water, together with Valoriza Agua and Sadyt, have studied the recycling process of disposed reverse osmosis membranes for reuse in nanofiltration and ultrafiltration processes. Throughout the project, experimentation has been carried out both at a laboratory scale and at a pilot scale, and very encouraging results have been obtained, which suggest that the membrane technology can be taken to a circular economy system.
Transformation is carried out by exposing the membranes to a concentrate solution of free chlorine. This chemical attack enables, by controlled conditions, to obtain nanofiltration membranes with a partial removal of the polyamide layer, or ultrafiltation membranes with the complete removal of the polyamide layer. To realise this membrane transformation two different methodologies have been developed: passive and active.
Within the framework of the LIFE TRANSFOMEM projects, recycled membranes have been validated successfully in three different applications: wastewater tertiary treatment, pretreatment of the reverse osmosis process, and softening of brackish water.
According to the experience of the LIFE TRANSFOMEM project, almost the 70% of the membranes are recyclable through this process, and the use of recycled membranes can save between 85% and 95% compared to the acquisition of new commercial membranes.
The membrane recycling process reduces greenhouse gas emissions and the consumption of non-renewable resources, helping to reduce the global impact of desalination on the environment.
The following video describes the work carried out in the LIFE TRANSFOMEM project and its main achievements:
TRANSFOMEM is a European Community co-funding LIFE project with contract number LIFE13 ENV/ES/000751