WESTERN PRODUCER — Industrial and urban wastewater is often a jumbled mixture of contaminated liquid, minerals, metals and nutrients — all valuable resources.
Much of Canada’s wastewater is urban effluent that has been treated and discharged into sewer systems. Industrial wastewater must be managed under federal regulations.
But if the minerals, metals and nutrient resources in wastewater could be extracted in a pure form, they would be invaluable for use in other industries such as agriculture, aquaculture, battery recycling and desalination.
Scientists at the Australian National University drew inspiration from how plants use their specialized molecular separation mechanisms to recognize and separate these resources for their own use. What if those biological mechanisms were adapted to use in new wastewater recycling technologies?
Caitlin Byrt, associate professor and plant scientist with ANU, said her research team was trying to figure out how to engineer crops to improve their tolerance to environmental stresses like drought and salinity, improve their yields and improve their energy and water-use efficiency.
They recognized that the knowledge gained on how plants use their mechanisms could be applied to the development of precision membrane separation technologies for industrial use. These mechanisms are used for filtering clean water from wastewater, concentrating substances through water extraction and removing contaminants.
Byrt said that these technologies are growing and expected to be worth about US$43 billion by 2028.
According to the news release, global wastewater contains three million tonnes of phosphorus, 16.6 million tonnes of nitrogen and 6.3 million tonnes of potassium. Recovering these nutrients in a pure form could offset 13.4 percent of global agricultural demand.
The Australian mining industry creates more than 500 million tonnes of waste per year, said Byrt. These wastes are rich in copper, lithium and iron. But the liquid waste is a problem because it cannot be dumped and cannot be used. It is waste until each resource can be separated out.
“This is particularly the case in the battery recycling space,” she said. “You have this huge, rich source of lithium inside dead batteries but we can’t yet extract or reuse it efficiently.”
She said that all living cells, including those in plants, are surrounded by a cell membrane, which can function like a barrier restricting what gets in or out.
“Plants are stuck in one place, which means that they have to source everything they need from the environment that they are directly in contact with,” she said. “To achieve this, plants take in liquids and gasses (that) contain complex mixtures of molecules. Plants then sort out the different molecules, identifying what they need and separating the molecules into different compartments to support cell metabolic needs. Plants use selective membrane separation mechanisms to achieve this sorting.”
This year, the research team is starting two large projects focused on taking the bio-engineered mechanisms they have been working on from laboratory testing to incorporation into prototype systems for testing in industrial settings.
“Every day, plants demonstrate their inherent capability to extract valuable materials from complex mixtures,” she said. “The amount of global precipitation each year is more than 100,000 kilometres cubed of water and around half of this passes through plants. Plants also take in around one-third of emissions of carbon dioxide but, if we do not look after the plants and ecosystems that perform this function, this capability will be lost.”
She said the ability of plants to use specialized molecular mechanisms to recognize and sort resources in the soil is likely an evolutionary development.
She said that there is a type of protein called an aquaporin that can be observed in most living cell membranes. Some single-celled organisms have one or two types of aquaporins, many mammals have around 13 types, but there are plant species that have evolved to have hundreds of different types of aquaporins.
“We are interested in the range of different types of solutes that different aquaporins can transport and how different types of mechanisms select for different types of substrates.”
The team has connected with a range of industry experts who manage liquid wastes and they are developing collaborative projects with colleagues with expertise related to agricultural wastes, mining wastes and urban wastes.
Byrt said there are innovative developments happening that include Canadian companies collaborating to optimize membranes for waste management in the oil and gas industry. Other organizations are partnering to provide solutions treating wastewater rich in nutrients.
The research was published in the journal New Phytologist.
