How Water Treatment Processes Release Aerosol Complexes
Imagine standing near a wastewater treatment facility or even along a picturesque coastline, taking a deep breath of what you assume is fresh air. Unbeknownst to you, that single breath may contain a complex mixture of chemicals and pathogens that began their journey in wastewater.
For decades, scientists have understood that water treatment is crucial for providing safe drinking water and protecting ecosystems. However, recent groundbreaking research has revealed a hidden pathway—where impurities believed to be contained in water literally take flight, transforming into airborne aerosols that create an invisible bridge between water pollution and air quality.
"This is the number one way that this pollution from the water is actually making its way into your body, even if you're not at the beach."
This article explores the cutting-edge science behind aerosol complexes generated in water treatment processes, a phenomenon that has remained largely unnoticed by the public despite its significant implications for public health and environmental protection.
At the heart of aerosol formation from water lies a deceptively simple process: bubble bursting. When air mixes with water—whether through waves crashing, aeration in treatment tanks, or mechanical agitation—it creates bubbles. As these bubbles rise to the surface and burst, they eject microscopic droplets of water into the air 2 .
Researchers at the University of Illinois Urbana-Champaign have systematically studied this phenomenon, explaining that when a bubble's cap ruptures, it triggers "Worthington jets"—tiny streams of fluid that eject aerosol droplets into the air 2 .
The bubble bursting mechanism becomes concerning when the water contains chemical or biological contaminants. Studies have confirmed that aerosols generated from contaminated water can carry a wide range of pollutants, including:
A compelling example of this phenomenon comes from recent research along the California-Mexico border. Scientists from the University of California San Diego have demonstrated that pollution from the Tijuana River doesn't just remain in the water—it becomes airborne.
The researchers found that when the polluted river water flows into the ocean and gets churned by waves, bubbles form and burst, releasing aerosols that contain chemical pollutants from the wastewater 1 .
Chemicals identified in coastal aerosols
Primary tracer for sewage (benzoylecgonine)
Potential wastewater chemicals in air
To truly understand how contaminants move from water to air, researchers designed a comprehensive field study near Imperial Beach, California—a community close to the mouth of the polluted Tijuana River.
Researchers chose multiple sampling locations near Imperial Beach, positioned at varying distances from the river mouth and along the coastline to account for wind patterns.
The team collected paired water and air samples during consistent meteorological conditions, particularly when winds were blowing from the ocean toward shore.
Scientists identified benzoylecgonine, a metabolite of cocaine found primarily in urine, as a specific tracer for sewage. This allowed them to distinguish aerosols originating from wastewater versus other sources 1 .
Using sophisticated laboratory techniques, the team analyzed samples for 12 specific chemicals commonly found in wastewater, including octinoxate (a sunscreen agent), pharmaceuticals like erythromycin, and industrial compounds.
The findings from the Imperial Beach study revealed several unexpected patterns that have reshaped our understanding of water-to-air pollution transport:
Of all compounds studied, octinoxate—a common ingredient in sunscreens and personal care products—showed the highest concentrations in both water and air samples.
While the concentrations of most other studied compounds were too low to represent acute health hazards, the researchers emphasized they investigated only 12 chemicals out of potentially thousands present in wastewater.
"There are potentially thousands of these different wastewater chemicals in the air. But an air monitoring infrastructure doesn't exist to quantify these pollutants, and there are no dedicated health monitoring resources to determine their impact on the community."
| Pollutant Category | Specific Compound | Primary Source | Relative Concentration in Aerosols |
|---|---|---|---|
| Personal Care Products | Octinoxate | Sunscreens, lotions |
|
| Pharmaceutical Compounds | Erythromycin | Antibiotics |
|
| Illicit Drugs & Metabolites | Benzoylecgonine | Cocaine metabolism |
|
| Industrial Chemicals | Dibenzylamine | Tire manufacturing |
|
| Pesticides/Herbicides | Diazinon | Agricultural runoff |
|
This table shows the diversity of wastewater-sourced chemicals detected in airborne aerosols near Imperial Beach, California. Adapted from Slade et al. (2025) 1 .
| Equipment Category | Specific Tool/Instrument |
|---|---|
| Aerosol Collection | High-volume air samplers |
| Water Sampling | Niskin bottles |
| Chemical Analysis | Gas chromatography-mass spectrometry (GC-MS) |
| Quality Control | Chemical standards |
| Meteorological Instruments | Anemometers, wind vanes |
| Parameter | Experimental Conditions |
|---|---|
| Bubble Size Range | 0.5-5 mm diameter |
| Contaminant Type | Silicone oil (experimental) |
| Oil Layer Thickness | Varied systematically |
| Jet Dynamics | High-speed camera analysis |
| Revised Ohnesorge Number | New parameter developed |
Parameters from controlled laboratory studies on bubble bursting mechanisms, showing the fundamental physics behind aerosol generation from contaminated water. Data from Feng et al. (2025) 2 .
Understanding aerosol formation and composition requires specialized equipment and methodologies. Here are the essential tools and reagents that scientists use to study aerosol complexes in water treatment processes:
These instruments measure aerosol light absorption at multiple wavelengths, allowing researchers to distinguish between different types of carbonaceous particles.
Precision instruments capable of detecting particles from 1 nanometer to 20 microns are crucial for characterizing aerosols .
To study the bubble bursting mechanism, researchers use high-speed photography capturing thousands of frames per second 2 .
Compounds like benzoylecgonine serve as effective sewage tracers because they uniquely originate from human waste rather than other pollution sources 1 .
Modern aerosol research increasingly uses drones equipped with particle counters to access difficult-to-reach areas .
This specialized software simulates the structural properties and evolution of aerosol particles 6 .
The discovery that water treatment processes and polluted water bodies generate complex aerosol mixtures represents a significant paradigm shift in environmental science. We can no longer consider water pollution as contained within aquatic ecosystems; instead, we must recognize that contaminants can cycle between water and air, potentially affecting communities far from the original pollution source.
"People living in the South Bay region, breathing in this air on a daily basis for years or decades, we have no clue to what extent this pollution is impacting their health, and that's a subject for future research."
The story of aerosols in water treatment processes serves as a powerful reminder that environmental systems are interconnected in ways we are only beginning to understand. As research continues to reveal these invisible bridges between water and air, we gain both a sobering appreciation of pollution's complexity and valuable insights that can lead to more effective protection of both human and environmental health.
References will be added here in the final version.