Duckweed is known for its remarkable ability to remove nutrients like nitrogen and phosphorus from water quickly and efficiently. It can even absorb certain metals and organic pollutants. But when wastewater is rich in sugars, oils, or fats, like many waste streams from the agri-feed industry, duckweed struggles to thrive on its own.
Take dairy processing wastewater, for example. This by-product from cheese, yoghurt, or milk powder production contains high levels of lactose, a sugar that duckweed can’t easily break down. So, does this limit duckweed’s potential in wastewater treatment and valorisation?
Absolutely not.
A Smarter, Two-Step Approach
At University College Cork, researchers from the NewTrients project have developed a clever two-stage system that combines the power of microbes and plants.
Step one: Acidogenic bacteria are used to convert lactose into valuable products such as volatile fatty acids (VFAs) and polyhydroxyalkanoates (PHAs). PHAs are key building blocks for bioplastics, offering a sustainable alternative to fossil-based plastics.
Step two: Once the lactose has been removed, the nutrient-rich wastewater is ideal for duckweed cultivation. Duckweed can then absorb remaining nitrogen and phosphorus while producing protein-rich biomass, perfect for use in animal feed.
This cascading approach turns a once problematic waste stream into a dual opportunity: bioplastics and animal feed right from rural industries.
From Dairy to Seafood: What’s Next?
As part of the IMPRESS project, the UCC team is now turning its attention to seafood processing wastewater, which is especially rich in polyunsaturated fatty acids (PUFAs), high-value compounds often used in health supplements.
The new goal? To design a cascading system that:
- First captures and recovers PUFAs for nutritional use
- Then employs duckweed to treat the nitrogen- and phosphorus-rich water that remains
This integrated approach opens exciting new pathways for resource recovery, sustainable aquaculture, and circular bioeconomy innovation.
References
O’Mahoney, R., Coughlan, N.E., Walsh, É. and Jansen, M.A.K, 2022. Cultivation of Lemna minor on industry-derived, anaerobically digested, dairy processing wastewater. Plants, 11(22), p.3027.
Walsh, É., Margassery, L.M., Rodriguez-Sanchez, A., Wall, D., Bolger, P., Jansen, M.A.K. and O’Leary, N., 2024. Integration of microbial bioreactors and Lemna minor cultivation for sustainable treatment of dairy processing wastewater. Journal of Water Process Engineering, 67, p.106290.
The article was written by University College Cork and edited by reframe.food.
All photographs in this article are sourced from University College Cork and Freepik.
