Ultra-clean Water Device To Help Grow Food For The Future

A new device that purifies water cheaply and efficiently could revolutionise hydroponic growing and make farming more sustainable in a changing world.

The photoelectrochemical water treatment device is being developed by a Te Whare Wānanga o Waitaha | University of Canterbury (UC) team led by Chemical and Process Engineering Professor Alex Yip, with funding from the Ministry of Business, Innovation and Employment.

Professor Yip says the goal of the project is to enable a climate change resilient food supply.

“Hydroponics, where plants grow in water instead of soil, is becoming an important technology internationally because it’s a way to grow crops in an environment protected from the increasing risks of storms, pests and disease. But it relies on ultra-clean water free from contaminants and pollutants.”

Professor Yip says if hydroponics is used to grow plants at scale in a developing country where the water is scarce and not completely clean, it can cause an accumulation of pollutants inside the plant called bioaccumulation.

“With a closed system with recirculating water, it is very important to keep the water clean, especially from emerging micropollutants, which is what we are targeting with our new device. These micropollutants include pesticides, endocrine-disrupting chemicals and long-lasting pollutants.”

The device the team is working on is unique and low-cost because it uses solar energy, reducing reliance on electricity.

“During the day, the smart device basically utilises solar light and converts it into chemical energy to remove pollutants from water,” Professor Yip says. “During night-time or under weather conditions where we don't have so much sunlight, it will automatically switch to an electrical system which powers the chemical reaction. This dual power source makes it more robust and adaptable to use.”

He hopes when the product is realised it can be marketed internationally, particularly to countries where clean water is not guaranteed.

The project team, which includes two PhD students - Chunyan Zeng and Vicky Tsui who is funded by the Joint Postgraduate School Food Transitions 2050 - has already found the device works in a laboratory setting, but it is currently being tested in a real-world hydroponic system.

Professor Yip says hydroponic farming is important because it has the potential to decarbonise the food chain. “If we can create an urban farm in a city centre, and perhaps grow food in a high-rise building, it means the produce doesn’t have to be transported long distances.

“Growing plants efficiently and sustainably within the city would help cut down some of the carbon emissions or ‘food miles’ associated with transportation. It would also mean that you can grow plants in winter or any time of the year, rather than just within the season for that fruit or vegetable, allowing off-season cultivation of high-value produce.”

While the photoelectrochemical water treatment device is designed to be used on a large scale, he says it could also be used in individual households instead of, or in addition to, water filters.

“Water filters are good to remove things that are not soluble in water, but the micropollutants we are talking about are much smaller than those captured by the filters.”

The team will seek further funding from the Government or private investors to scale up the project once testing is complete. “We are really excited about it and hoping that in a few years’ time, we’ll see the product in the market,” Professor Yip says. “Our intention is to make it affordable for hydroponic farming operations of all sizes.”

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