Contaminants from everyday products like plastics, pharmaceuticals and industrial chemicals find their way into and pollute rivers, soils, oceans and drinking water supplies around the world. Though approximately 350,000 synthetic chemicals are registered for production and use worldwide, less than 1% are systematically regulated, leaving their environmental impact largely unaddressed.
A new study from researchers at the University of Illinois suggests that wastewater treatment systems could play a key role in mitigating the growing impact.
Published in Nature Communications, the study found that wastewater residual solids – the concentrated solids removed from wastewater during treatment – capture substantial amounts of emerging contaminants, making wastewater treatment facilities ideal intervention points to eliminate pollutants from the environment.
The research was led by Jianan Feng and Jeremy S. Guest in the Department of Civil and Environmental Engineering at The Grainger College of Engineering.
“Many emerging contaminants become extremely difficult to manage once they disperse throughout the environment,” said Guest. “Our work shows that wastewater treatment systems already collect a meaningful fraction of these contaminants into a much smaller and more manageable stream. That creates an opportunity to intervene before they spread into rivers, soils, groundwater, and ecosystems.”
To assess the concentration of pollutants found in wastewater residual solids, Feng and Guest compiled global datasets for three common contaminants: microplastics, pharmaceuticals, and antibiotic resistance genes. Their analysis showed the concentration of each is often much higher in residual solids than typically found at any one place in the environment, with global transmission models revealing that approximately 20% of microplastic emissions, 24% of pharmaceutical emissions, and 13% of antibiotic resistance gene emissions pass through residual solids in their lifecycle.
This convergence of several problematic contaminants emphasizes the strategic opportunity for intervention.
“Rather than viewing wastewater treatment plants solely as facilities for protecting water quality, we can begin to think of them as part of a broader environmental protection network,” said Feng. “These systems already serve hundreds of millions of people worldwide and could become an important line of defense against a wide range of contaminants.”
Knowing that wastewater residual solids function as contaminant sinks, the researchers also sought to determine which treatment method most efficiently removes pollutants. They took particular interest in thermochemical techniques, which rely on heating the solids to extreme temperatures to destroy contaminant molecules. In comparison to traditional methods, they found that thermochemical treatment achieved near-complete destruction of the contaminants.
The final phase of the study examined technoeconomic and environmental analyses of over 4,700 wastewater treatment facilities in 105 countries to assess the feasibility of adopting thermochemical technology. The researchers found strong environmental incentives, namely that thermochemical processes produce significantly lower greenhouse gas emissions than traditional methods but saw that financial and deployment practicality differed across global regions.
Overall, Guest and Feng’s research outlines the potential for wastewater systems to act as a first line of defense against new and emerging contaminants on top of the crucial role they play protecting communities from traditional pollutants.
“Twentieth-century sanitation systems transformed public health by reducing the spread of pathogens,” Guest said. “This work suggests that twenty-first-century wastewater systems could evolve to play a similarly important role in protecting environmental and public health from emerging contaminants.”
The study, “Thermochemical Treatment of Wastewater Residual Solids for Global Mitigation of Emerging Contaminants,” was published in Nature Communications. The research was supported by the National Science Foundation and conducted within the Department of Civil and Environmental Engineering at the University of Illinois Urbana-Champaign.