Natural Water Purification Inspired by Ocean Diatoms

Innovation: Industry

Retein

2021

Image: Anastasia Taioglou / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Capture, Absorb, or Filter Solids

Some living systems must secure solid particles such as sediment, usually to keep the particles from hindering their health or activity. The most common way in which they do this is through filtering. To be effective, a filtering system must be appropriate to the sizes of solid particles to be captured and must capture only what is needed. It must also be effective in the appropriate media–air, water, or sometimes solids like soil. An example is mangroves, which are trees that grow along ocean coasts. Their root system slows down and settles sediment out of the water, building up soil to support the mangrove ecosystem.

Search this Function

Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

Search this Function

Retein stabilizes aquaporins in lipids and silica to desalinate and purify water.

Benefits

Improved water treatment and re‑use
Reduced energy use

Applications

Industrial wastewater treatment

UN Sustainable Development Goals Addressed

Goal 3: Good Health & Wellbeing
Goal 6: Clean Water & Sanitation
Goal 14: Life Below Water
Goal 15: Life on Land

The Challenge

Water scarcity affects every continent, with more than 2 billion people lacking access to safe drinking water. Small, harmful pollutants, such as pharmaceutical residues, pathogens, and microplastics, are wreaking havoc in our oceans, lakes, and rivers. And although we have powerful water purification systems, forcing millions of gallons of water through the membrane of a filter takes a significant amount of energy. So, if we want a higher purity of water we must use a higher energy input, therefore pumping more carbon dioxide into the atmosphere, and creating a much greater cost for clean water.

Innovation Details

Retein is on the cusp of revolutionizing the water purification industry. The team is mimicking the way diatoms form their cell wall out of silica and utilizing aquaporins, proteins that transport pure water across cell membranes throughout nature. Their energy-efficient and selective technology produces high purity grade water in a single filter pass, desalination at any scale, and removes industrial pollutants and contaminants such as arsenic, microplastics, and pharmaceutical residues.

Watch how the team at Retein (formerly Aquammodate) was inspired by diatoms and aquaporins to create a biomimetic method for water purification.

Biological Model

Water is an indispensable component of living cells—in a Goldilocks sort of way. Too much and the cell will burst; too little and it will dry out and die. How does a cell keep its water content just right? It makes aquaporin molecules that form hourglass-shaped tunnels through its otherwise water-repelling membranes. Electrical charges inside the tunnels ensure that only water (and sometimes a few select other molecules) can get through, and only in small amounts, maintaining the balance needed to maintain life.

To embed aquaporins in a stable, usable material for humans, Retein looked to single-celled organisms found in lakes, rivers, and oceans around the world. Diatoms use special proteins to draw the mineral silica from water into a sac inside their cell. There, other proteins link the silica atoms together to form the hard surfaces. Yet other proteins connect the hard parts to form a box around the cell and to make a pinch point that holds them together. Sugar and other organic materials add yet more stability and create different shapes for different species.

EXPLORE THESE BIOLOGICAL STRATEGIES

Biological Strategy

Hourglass-Shaped Molecules Filter Water

Common to all organisms

Aquaporin molecules form a channel that allows water to move across cell membranes.

black and white microscopic view of a diatom

Biological Strategy

Diatoms Build Glass Houses That Are Stable and Strong

Diatoms

Diatoms build strong, intricate cases using proteins to arrange minerals.

Ray of Hope Prize

Retein (formerly Aquammodate) was selected as the runner up for the 2021 Ray of Hope Prize, which celebrates nature-inspired solutions addressing the world’s biggest environmental and sustainability challenges. Created in honor of Ray C. Anderson, founder of Interface, Inc. and a business and sustainability leader, the $100,000 Ray of Hope Prize helps startups cross a critical threshold in becoming viable businesses by amplifying their stories and providing them with equity-free funding. The prize shines a light on the innovative, nature-inspired solutions that we need to build a sustainable and resilient world.

AskNature