The Beginning of a Promising Future
The demand for safe drinking water is outgrowing the planet’s natural supply at an alarming rate. At the same time the world has already begun experiencing the impacts of global climate change, driven by unsustainable energy practices, which will have increasing negative impacts on fresh water availability. There is therefore an urgent need for affordable, low energy desalination solutions capable of addressing the water crisis.
The REvivED water project, a research and innovation project funded under the EU’s Horizon 2020 programme in the field of ‘low-energy solutions for drinking water’ which ran from 2016 to 2020, has taken great strides in advancing desalination technology and understanding towards addressing this need. The project brought together extensive partner experience to develop innovative technologies and applications for electrodialysis in desalination.
In electrodialysis, an electric current is applied to salty water, causing the salt ions to pass through ion exchange membranes, leaving desalinated water behind. This technology can have in principle lower energy requirements than reverse osmosis. It is also more resilient to power fluctuations and therefore more readily adaptable to direct connection with renewable energy sources such as solar and wind power. REvivED water recognised the potential of this technology to be implemented in varying ways across the highly diverse water supply sector and so targeted three distinct applications: small standalone units for desalinating brackish water, large-scale multi-stage units for seawater desalination and the integration of electrodialysis units with existing reverse osmosis systems to improve energy efficiency.
Overall, the REvivED water project has laid the groundwork for several promising options for electrodialysis in the future of desalination. The ground-breaking research, new technologies and methods, innovative dynamic modelling and remote operating systems are all important steps towards a future where safe drinking water is easily accessible, low cost and significantly less energy-intensive.
Safe Water from Brackish Sources
Beginning in 2018 the project began installing small standalone desalination systems for rural areas powered by solar energy. These novel systems incorporated new designs and technologies developed by the partners in the project and proved effective at treating brackish water of varying salinities. Although the project is now concluded, seven of these units are still operating in rural communities in East Africa and India and spare parts have been set aside for each units’ maintenance post-project.
The success of these units has opened up a hopeful front in the battle against dwindling fresh water resources in remote areas with logistic and environmental challenges. These units were the subject of a Smarter E award that was presented to partner Phaesun. Several project partners have active plans for follow-on work that will focus on standardising the manufacture of these units and making them commercially affordable to those communities that need them most. Their efficiency and remote-capable operation also provides potential add-on options for incorporating further amenities that might be otherwise difficult to secure in these areas.
Electrodialysis for Seawater Desalination
In an effort to develop an alternative seawater desalination solution, the latest innovations in ion exchange membranes and stacks were incorporated into a novel multi-stage electrodialysis system. REvivED water researchers applied reverse electrodialysis (RED) as a pre-desalination step on an industrial-scale pilot electrodialysis unit. This approach can be used when a low salinity water stream is also available. This reduces the desalination load on the main electrodialysis process without requiring any energy input.
The 25 m3/day pilot (R)ED unit is currently being successfully run with seawater at Afsluitdijk in the Netherlands and has demonstrated the core concepts of this method. While this process shows promise for eventual implementation in the drinking water industry, the partners of REvivED water have also been examining how it might benefit industrial extraction and production technologies, many of which require fresh water for separation and other processes. Early adopters in these sectors would not only reduce the overall energy and fresh water cost of certain products, but would also help accelerate the continued development of (R)ED technology for implementation in the drinking water sector.
Integration with Established Technologies
Reverse osmosis is a more established technology and its use is widespread, particularly within the drinking water and water reclamation sectors. REvivED water scientists therefore explored ways in which their research might improve the overall efficiency of established reverse osmosis plants in order to reduce the economic and carbon footprint of desalination in general. They designed an electrodialysis unit that can be installed as a pre-desalination step in existing reverse osmosis systems. Their tests have demonstrated that their unit can allow a reverse osmosis system to make more drinking water from the same amount of seawater while consuming less overall energy.
In 2019 the project demonstrated the potential of this arrangement through a 25 m3/day seawater desalination unit that was installed in an active wastewater treatment plant, operated by the company FACSA in Burriana, Spain. The treated wastewater has been used to demonstrate the option of adding a reverse electrodialysis (RED) pre-desalination step. The success of this trial has shown promise for further development and several partners have discussed plans for the next steps in commercialising this technology, such as standardised manufacturing, targeted markets and expanded trials.