PROJECT DESCRIPTION
BACKGROUND
The main technologies for the desalination of seawater are thermal evaporation (distillation) and reverse osmosis (RO). The world market for RO water treatment systems has grown rapidly, for example, from an estimated $1.4 billion in 2000 to $3.8 billion in 2008.
Unfortunately, there can be high environmental costs and the energy required to produce RO water is about 10 times more than for conventional water distribution. There are currently more than 15 000 desalination plants operating in 100 countries. Of these, 80% use polymer-based membrane technologies, nearly 90% of them based on reverse osmosis. The RO membranes used in this process reach their end-of-life typically between 5 and 10 years, resulting in costly waste which is sent to landfill. In Spain alone, around 100 000 RO membranes need replacing each year. The recovery of RO membranes, using novel mechanical and chemical treatments, for reuse in the desalination process or in other applications which need a lower-quality water specification (e.g. wastewater treatment for irrigation or industrial water with low salinity requirements) could bring considerable financial and environmental benefits.
OBJECTIVES
The REMEMBRANE project aimed to prolong the lifecycle of membranes used in reverse osmosis (RO) saltwater treatments, through an innovative technology to improve membrane recovery that enables their re-use. The objective was to avoid waste, reduce costs and improve the overall efficiency of the desalination process. A mobile demonstration plant was planned to develop diverse mechanical and chemical treatments for any RO membrane recovered at end-of-life. These membranes should be suitable for re-use in the same desalination process or in other RO applications needing a lower-quality water specification, such as irrigation. As part of the pilot project, the project aimed to build a compact, portable testing unit to perform trials on the recovered membranes at real installations.
RESULTS
The REMEMBRANE project optimised a system for recovering worn-out reverse osmosis (RO) membranes for re-use. The project beneficiaries designed and constructed a pilot RO membrane recovery plant at the Racons desalination facility in Dénia, Alicante (Spain). The recovered RO membranes were tested in the wastewater treatment plant (WWTP) in the Spanish city of Talavera de la Reina and at a desalination plant operated by AQUALIA.
At the start of the project, the team analysed the current global status of desalination, to better evaluate project impacts and benefits. They established indicators to assess the viability of the project, the legal framework, and the processes to clean and recover membranes depending on the level of soiling. In total, the project team collected used RO membranes from seven different locations. They carried out autopsies and lab tests on these membranes, to optimise the design of the pilot plant for cleaning the membranes. After the trials at the pilot recovery plant, they estimated that 80% of the membranes could be recovered for use as RO membranes. The irretrievable membranes could still be used as part of other less demanding processes (e.g. brackish water treatment for irrigation).
The average cost of recovering a membrane was €100 (capacity 6 membranes). This entails savings of, at least, €250/membrane, which will increase when the technology is up-scaled. The average cost per membrane for a plant with a treatment capacity of 30 membranes is estimated at €45. This could also imply a significant reduction in the costs of constructing treatment plants and their operation. This is due to the fact that the RO is a very expensive technology, mainly due to the price of new membranes (€350-400/membrane for large desalination plants). Pre-treatments currently used to protect RO membranes from burnout would also no longer be necessary. Consequently, this technology could contribute to widening the reuse and desalination of water, since it would be much more cost-efficient.
As a result of the project, expertise was gained in RO membrane management, which is vital when replicating the technology. The project team trained workers in the use of the membrane recovery technology (a valuable new green skill in this sector). The recovered RO membranes are also more resistant than given in their original product specifications. This is very important for companies involved in reverse osmosis WWTP management, since the membranes are considered one of the most fragile elements of the system and extra resources and efforts are devoted to handling them.
A life-cycle analysis (LCA) showed that the REMEMBRANE solution is better from an environmental point of view than the production of new membranes. For instance, fewer membranes will be disposed of in landfills, as they are being reused. In Spain alone, estimates suggest that this could amount to approximately 6 700 tonnes of membranes per year. Furthermore, the use of recovered membranes in wastewater treatment plants reduces the cost of regenerated water, of particular importance in arid and semi-arid areas where water scarcity is a major issue. This could result in major socio-economic benefits.
The project is directly relevant to water reclamation policy, mainly the Water Framework Directive (2000/60/EC), by widening the use of reclaimed water and making it more affordable. The project also supports the principles of the Waste Framework Directive (2008/98/EC) and circular economy policy by turning a waste into a resource. AQUALIA is using the project’s innovative technology to launch a new business line aimed at recovering end-of-life reverse osmosis membranes. It is foreseen that a 5% growth per year may be a reasonable objective until 2020. This could create jobs in Spain, and elsewhere in the EU, as the technology is transferred and replicated.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
