Single-pass water filtration Aquammodate – Filtration + Separation

Prototype of Aquammodate membrane being tested in the laboratory. (Image: Aquammodate)
The technology emulates how diatoms mechanically stabilize their cell membranes by forming a silica cell wall.  (Image: Wikipedia / Wiper)
The technology emulates how diatoms mechanically stabilize their cell membranes by forming a silica cell wall. (Image: Wikipedia / Wiper)
Diatoms build their cell walls from silica for mechanical protection.  (Image: Flickr / @spacenoob)
Diatoms build their cell walls from silica for mechanical protection. (Image: Flickr / @spacenoob)
Color electron microscopy of a diatom.  (Image: Flickr / @ zeissmicro)
Color electron microscopy of a diatom. (Image: Flickr / @ zeissmicro)

A Swedish start-up creates water filtration inspired by diatoms and aquaporin proteins. Recently named by the Biomimicry Institute as a finalist in its Ray of Hope Prize competition, Aquammodate’s selective technology produces pure water with a single pass of the filter and desalination at any scale.

The Ray of Hope Prize program, organized by the Biomimicry Institute, a non-profit organization founded in 2006, supports start-ups working to tackle the world’s biggest sustainability challenges with solutions inspired by the nature. The program helps them effectively communicate the science behind their work and teaches them about sustainable business practices such as green materials and circular business models.

The Biomimicry Institute believes that to be truly sustainable, the world needs products, processes, and systems that mirror what is found in nature. The Ray of Hope Award is a key initiative of the Biomimicry Institute and the Ray C. Anderson Foundation, honoring Ray C. Anderson, a sustainable business pioneer who used the concepts of business biomimicry to create more respectful of the environment and more efficient.

Swedish company Aquammodate was named a finalist, one of 10 finalists for the 2021 Ray of Hope Prize, winning US $ 25,000. It is based in Gothenburg, Sweden and its patent pending water purification technology was developed during a doctoral project at Chalmers University of Technology in Gothenburg.

Bio-inspired method
Aquaporin proteins are water channels that selectively facilitate the transport of water across the cell membrane of all living cells in an energy efficient manner. Aquammodate has developed a bio-inspired method to stabilize aquaporins in order to use their extraordinary characteristics in water purification and treatment processes. The main stabilizing components are lipids and silicon dioxide (silica). Lipids are dual purpose as they both mimic the natural environment of aquaporins and act as the semi-permeable component in the filter. Silica gives biological components mechanical and chemical robustness while preserving their structure.

Aquammodate technology harnesses the characteristics of diatoms and aquaporin proteins and has the potential to produce high purity water with a single pass of filter, desalination at any scale and remove pollutants and contaminants such as arsenic, microplastics and pharmaceutical residues. Company CEO and Co-Founder Simon Isaksson said, “Our technology matches the Ray of Hope Prize innovation criteria inspired by nature in two main ways. First, it emulates how nature’s finest water purification is carried out through the cell membrane and second, it emulates how diatoms mechanically stabilize their cell membranes by forming a silica cell wall.

How the technology works
He went on to explain, “Some aquaporins only carry water and are said to be orthodox, this is the type of aquaporin that we use in our solution. In nature, water is transported through aquaporin as a result of an osmotic gradient, which moves water from the region of low osmolarity (mostly solute concentration) to higher osmolarity. As a result, no external pressure is applied, instead there is a tensile force.

“Aquaporins are selective for water molecules over all other molecules because the channel contains an electrostatic barrier in combination with a narrow passage. Specific amino acids in the wall of the channel interact in a very specific way with water molecules. These interactions align the water molecules to move them through the aquaporin channel in a single file.

The main difficulty with using aquaporins (and biological components in general) outside their original environment is that they easily lose their structure and therefore their function. Applying an external pressure such as that used in reverse osmosis will break up the self-assembled structures (lipid bilayer) that harbor the aquaporins, causing their structural collapse.

Aquammodate uses the properties of diatom to stabilize aquaporins for use in applications outside of their native environment. Diatoms build their cell walls from silica for mechanical protection. The cell wall is located just outside the cell membrane where aquaporins and other membrane proteins are found.

Isaksson continued, “Although the complete process of forming diatomaceous silica is not yet understood, it has been established that they absorb silicic acid from surrounding water as the first step in the process. They then polymerize these building blocks in silica which is then transported outside the cell membrane. Our technology also starts with silicic acid which it polymerizes into silica, but the company’s polymerization occurs directly outside the lipid membrane containing the aquaporin.

“Once stabilized, our current approach is to integrate the constructs containing aquaporin into the polymeric reject layer of conventional reverse osmosis membranes. The idea behind this approach is that these silica stabilized aquaporins will provide a low resistance channel through the RO membrane only for water with the ability to overcome the inherent permeability-selectivity tradeoff to which current RO membranes are subjected. This is because nature’s best water filtration has the ability to carry 100% pure water at 100 times the flow rate of current RO membranes.

The future
Aquammodate is currently testing the performance of prototype membranes in the laboratory, where aquaporins stabilized with silica are integrated into polymer membranes. It is also co-developing membranes with existing membrane manufacturers and the company plans to begin pilot-scale testing towards the end of 2021 and will continue to work with co-development partners towards the introduction on the Marlet.

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