From waste to clean water using sunlight

Dr. Akanksha Menon

We all think of oil and gas companies as energy companies, but what if I told you their biggest product is water? Or wastewater, to be more precise.

This is because the production of one barrel of oil is accompanied with over 10 barrels of water, and given that these companies produce over a million barrels of oil in a single day, you can just imagine the scale of the wastewater challenge!

Since this water is too contaminated to be reused, it is typically disposed of by injecting it deep into underground wells. Last year, scientists conclusively showed that deep well injection was causing seismic activity in regions with no earthquake history – like Oklahoma, for example.

So this may make you wonder – instead of disposing this wastewater, can we purify it to meet the growing demand for clean water? The answer is yes, and this is the focus of my research. We’re developing a desalination technology to separate salts and contaminants from water.

There’s thermal desalination, where huge amounts of heat are used to evaporate water leaving salts behind, and there’s membrane desalination, where you use large amounts of electricity to force water across a selective membrane that blocks the salt out. This is the crux of the problem – desalination requires a tremendous amount of energy especially when it has to be done at a large scale.

To address this, we’re developing a system powered by solar energy to power a hybrid membrane-thermal desalination process. Typically, when we think of solar, we think of PV panels that convert sunlight into electricity. Instead, we are converting sunlight into infrared heat to drive the purification process.

Our secret sauce is a temperature-responsive material that performs two critical functions – it draws water across the membrane, separating it from the salts, and then itself separates from the water by absorbing this infrared heat. This separation process requires virtually no electricity and the thermal energy consumed is 1000x lower than evaporating water.

I am excited to share that we have successfully demonstrated this at the lab-scale and will be working with our industrial partners to field test the technology here in California. Thus, by transforming this waste into a resource, we can minimize the environmental impact of wastewater disposal, as well as close the water loop by recycling water for agriculture and potable reuse – all by harnessing the power of our sun.