New Hydrogel Turns Toxic Wastewater and Algae Blooms into Garden Gold

Picture a super-absorbent gel that could turn sewage into plant food while preventing toxic algae blooms.

That’s exactly what engineers at Washington University in St. Louis have created—a new hydrogel technology that simultaneously removes harmful nutrients from wastewater and transforms them into valuable agricultural fertilizers. The breakthrough addresses a pressing environmental crisis that costs the U.S. economy up to $81.6 million annually in harmful algal bloom damage alone.

The innovative system works like the moisture-absorbing core of a disposable diaper, but with a twist. Instead of just soaking up water, these special hydrogels capture excess ammonia and phosphate from wastewater—the very nutrients that trigger devastating algae blooms in lakes, rivers, and coastal waters.

The Toxic Twin Problem

Excessive nutrients in wastewater create a dangerous domino effect in natural water systems. When ammonia and phosphate flow into rivers and lakes, they act like fertilizer for algae, sparking explosive growth that produces harmful toxins. These blooms devastate marine ecosystems and contaminate drinking water supplies.

But here’s the irony: while these nutrients poison waterways, farmers desperately need them for crops. Ammonia production requires enormous amounts of energy, and global phosphorus reserves are steadily shrinking. This creates an expensive paradox—we’re spending billions to remove nutrients from wastewater while simultaneously mining and manufacturing the same compounds for agriculture.

Engineering Nature’s Solution

Young-Shin Jun, a professor of energy, environmental and chemical engineering, and doctoral student Minkyoung Jung developed mineral-hydrogel composites embedded with nanoscale “seeds” made from calcium phosphate and struvite—a naturally occurring mineral containing magnesium, ammonium, and phosphate.

The process mimics how rock candy forms on a string. Just as sugar crystals grow around a seed crystal, nutrients in wastewater bind to these mineral seeds and gradually bulk up the hydrogel. During treatment, the average particle sizes increased from 6.12 nanometers to 14.8 nanometers as they collected nutrients.

“We designed these hydrogel composites to recover ammonia and phosphate, essential nutrients whose overabundance causes algal bloom,” Jun explained. “Ammonia synthesis is energy-intensive, and phosphorus resources are dwindling. Our mineral-hydrogel composites allow us to harvest these nutrients from wastewater and repurpose them as fertilizers and feedstock for biorefineries.”

Impressive Removal Rates

The technology tackles three critical challenges that have long plagued conventional nutrient removal methods:

• Inefficient collection using traditional techniques
• Difficulty balancing simultaneous removal of both ammonia and phosphate
• Maintaining consistent removal efficiency in complex, real-world water conditions

The results speak for themselves. The hydrogel composites removed up to 60% of ammonia and an impressive 91% of phosphate from wastewater samples. This dramatic reduction effectively prevents the formation of harmful algal blooms while capturing valuable nutrients for reuse.

From Lab Bench to Real World

What makes this research particularly promising is its scalability potential. Jun’s team has already successfully tested the process on volumes up to 20 liters and is now scaling up to 200-liter trials—a significant step toward commercial viability.

The technology also offers environmental advantages over existing methods. Unlike traditional approaches that rely on energy-intensive chemical processes or generate significant waste, this system operates through natural crystallization processes with minimal environmental impact.

“This demonstrates the practical application potential of our fundamental scientific research, showing a viable path from the laboratory to everyday technology,” Jun noted. “This pioneering work represents a significant advancement in environmental engineering, turning a waste problem into a valuable resource and exemplifying sustainability in action.”

The Circular Economy Connection

The research, published in Environmental Science & Technology’s special issue on “Advancing a Circular Economy,” exemplifies how innovative engineering can solve multiple problems simultaneously. Rather than viewing wastewater nutrients as waste requiring expensive removal, this approach reframes them as valuable resources awaiting recovery.

This shift in perspective could reshape how society handles wastewater treatment. Instead of costly disposal, treatment facilities could become nutrient recovery centers that generate revenue from recovered fertilizers while protecting waterways from pollution.

The technology has already attracted attention from Washington University’s Office of Technology Management, which has filed patents to protect the mineral hydrogel innovation. Funding from the U.S. Environmental Protection Agency and Department of Energy supported the research, underscoring government interest in sustainable waste treatment solutions.

Addressing Global Food Security

Beyond environmental benefits, this technology could help address growing global food security challenges. With world population expected to reach nearly 10 billion by 2050, sustainable nutrient recovery becomes increasingly critical for feeding the planet without depleting natural resources.

Traditional phosphorus mining faces mounting sustainability concerns, while energy-intensive ammonia production contributes significantly to global carbon emissions. Technologies that recover these nutrients from waste streams offer a more sustainable path forward.

The recovered materials can serve dual purposes—as traditional agricultural fertilizers or as specialized feedstock for biorefineries that produce biofuels and other valuable products. This versatility makes the technology attractive for diverse applications across multiple industries.

As climate change intensifies pressure on food systems and environmental regulations become stricter, innovations like these hydrogel composites may prove essential for creating truly sustainable waste treatment and agricultural systems. The technology demonstrates that sometimes the best solutions come from viewing waste not as a problem to eliminate, but as a resource waiting to be harvested.