Excessive nutrients in wastewater can result in harmful discharges into natural water systems, leading to toxic algal blooms with significant environmental and economic consequences. To tackle this urgent concern, a group of engineers at the McKelvey School of Engineering at Washington University in St. Louis has crafted an inventive solution. Their cutting-edge composite nanotechnology extracts and recovers nutrients from wastewater, subsequently upcycling them for use as agricultural fertilizers or biorefinery feedstocks, while concurrently reducing the likelihood of harmful algal blooms.
Young-Shin Jun, a professor specializing in energy, environmental, and chemical engineering, along with Minkyoung Jung, a Ph.D. student working in her lab, devised pioneering mineral-hydrogel composites capable of extracting and recovering ammonium and phosphate from wastewater. These composites incorporate nanoscale struvite and calcium phosphate mineral seeds, which considerably decrease ammonia and phosphate levels in wastewater by as much as 60% and 91%, respectively. This reduction helps to limit algal proliferation and the related toxins. A 2000 report by the U.S. National Oceanic and Atmospheric Administration estimated that the economic costs from harmful algal blooms in U.S. coastal waters ranged from $33.9 million to $81.6 million annually, highlighting the potential impact of this technology.
Findings from the study were published online on May 29 in a special edition of Environmental Science & Technology.
Similar to the moisture-retaining gel used in disposable diapers, this hydrogel can absorb and repurpose excess nutrients. For their sustainable solution, Jun’s team utilized nature as both an inspiration and a beneficiary of their technique.
“We engineered these hydrogel composites to extract ammonia and phosphate, vital nutrients whose excess contributes to algal blooms,” Jun stated. “Synthesizing ammonia requires substantial energy, and phosphorus resources are depleting. Our mineral-hydrogel composites enable us to reclaim these nutrients from wastewater and convert them into fertilizers and feedstocks for biorefineries.”
The technique employs nanoparticle nucleation — the initial phase in forming a solid state in a liquid environment, akin to the process where sugar crystals form on a string to create rock candy. To enhance that process, Jun’s team embedded minuscule mineral seeds in the hydrogel made from calcium phosphate and struvite, a mineral comprising magnesium, ammonium, and phosphate that associates with calcium and other cations and ions. The ammonia and phosphate attach to the seeds, enlarging the hydrogel. During these processes, the average particle sizes of the hydrogel increased from 6.12 nanometers to 14.8 nanometers.
Their approach tackles three major challenges of traditional nutrient removal: ineffective collection in standard techniques; balancing the removal of both ammonia and phosphate; and ensuring consistent removal efficiency in complicated water conditions. This method achieves extraordinarily low nutrient levels, effectively hindering harmful algal blooms.
Jun emphasized the scalability of the process, with successful trials conducted on up to 20 liters of liquid. The lab is now expanding to handle 200 liters.
“This illustrates the practical application potential of our foundational scientific research, showcasing a feasible transition from the laboratory to everyday technology,” Jun remarked. “This groundbreaking work signifies a notable progress in environmental engineering, transforming a waste challenge into a valuable resource and exemplifying sustainability in action.”
Jun collaborated with WashU’s Office of Technology Management to secure a patent for the mineral hydrogel technology.
Jung M, Wang Y, Ilavsky J, Tang Y, Jun Y-S. Molecular insights into novel struvite-hydrogel composites for simultaneous ammonia and phosphate removal. Environmental Science & Technology, online May 29. https://pubs.acs.org/doi/10.1021/acs.est.4c11700
Funding for this research was provided by the U.S. Environmental Protection Agency and the U.S. Department of Energy.
Originally published on the McKelvey Engineering website
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